how can i unlock a picture file that was loaded in a picturebox in visual c#?

I am developing a mini game in which the user must recognize the person's face and type in that person's name. Each picture is "saved" in a folder with the person's name, so the game uses both the picture and the filename... This is my code :

using System;
using System.Threading;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;


namespace FaceNameGame
{
    public partial class LevelOnePartTwo : Form
    {
        int point = 0, buttoncount = 0, i=0, h=3, hbuttoncount=0;
        public LevelOnePartTwo()
        {
            InitializeComponent();
        }

        private void LevelOnePartTwo_Load(object sender, EventArgs e)
        {

            string[] files = Directory.GetFiles(@"C:\Users\Marina\Desktop\FaceNameGame\images\Level1\used", "*.jpg", SearchOption.AllDirectories);
            PhotoPicBx.Load(files[i]);
            NameTxtBx.Focus();
            Pointlbl.Text = point.ToString();
            

        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void PhotoPicBx_Click(object sender, EventArgs e)
        {

        }

        private void TemplatePicBx_Click(object sender, EventArgs e)
        {

        }

        private void Hintbtn_Click(object sender, EventArgs e)
        {
            hbuttoncount++;
            h--;
            string nameused21 = PhotoPicBx.ImageLocation.ToString();
            string nameused22 = nameused21.Substring(nameused21.LastIndexOf("\\"));
            string nameused23 = nameused22.Remove(nameused22.Length - 4, 4);
            string nameused24 = nameused23.Remove(0, 1);
            string nameused2h = nameused24.Remove(nameused24.Length - h, h);
            NameTxtBx.Text = nameused2h;
            
            if (point > 0 && h>=0)
            {
                point = point - 5;
                Pointlbl.Text = point.ToString();
            }

            if (h <= -1)
            {
                h = 0;
            }

            if (hbuttoncount == 3)
            {
                Hintbtn.Hide();
            }
        }

        int s = 0;
        private void timer1_Tick(object sender, EventArgs e)
        {
            s++;
            int m = s / 60;
            int h = m / 60;
            Timelbl.Text = "" + h.ToString() + " : " + m.ToString() + " : " + s.ToString();
        }

        private void Checkbtn_Click(object sender, EventArgs e)
        {

            string nameused1 = PhotoPicBx.ImageLocation.ToString();
            string nameused2 = nameused1.Substring(nameused1.LastIndexOf("\\"));
            string nameused3 = nameused2.Remove(nameused2.Length - 4, 4);
            string nameused = nameused3.Remove(0, 1);

            int comp = NameTxtBx.Text.CompareTo(nameused);


            if (comp == 0)
            {
                point = point + 50;
                Pointlbl.Text = point.ToString();
                NameTxtBx.Text = "";
                buttoncount++;




                if (buttoncount <= 2)
                {
                    if (i < 2)
                    {
                        i++;
                        string[] files = Directory.GetFiles(@"C:\Users\Marina\Desktop\FaceNameGame\images\Level1\used", "*.jpg", SearchOption.AllDirectories);
                        PhotoPicBx.Load(files[i]);
                        NameTxtBx.Focus();
                        h = 3;
                        hbuttoncount = 0;
                        Hintbtn.Show();

                    }

                }
            }

            int pointcount = Int32.Parse(Pointlbl.Text);


            if (buttoncount > 2)
            {

                SqlConnection sqlConnection1 = new SqlConnection("Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=C:\\Users\\Marina\\Desktop\\FaceNameGame\\facenamegame\\mygamedb.mdf;Integrated Security=True;Connect Timeout=30");
                System.Data.SqlClient.SqlCommand cmd = new System.Data.SqlClient.SqlCommand();
                cmd.CommandType = System.Data.CommandType.Text;
                DateTime time = DateTime.Now;              // Use current time
                cmd.CommandText = "insert into Userrecords (Username, Points, Logindate,Level) values(@Username, @Points, @Time, 'Level 1')";
                cmd.Connection = sqlConnection1;





                {


                    cmd.Parameters.AddWithValue("@Username",LoginInfo.UserID );
                    cmd.Parameters.AddWithValue("@Points", pointcount);
                    cmd.Parameters.AddWithValue("@Time", time);
                   
                



                    sqlConnection1.Open();
                    cmd.ExecuteNonQuery();
                    sqlConnection1.Close();
                   
                }


                if (pointcount >= 130)
                {
                    LevelOneSuccessScreen lvlonesucscreen = new LevelOneSuccessScreen();
                    lvlonesucscreen.Show();
                    this.Close();
                }

              if (pointcount < 130)
                {
                    LevelOneRepeatScreen lvlonerepscreen = new LevelOneRepeatScreen();
                    lvlonerepscreen.Show();
                    this.Close();
                   
                }
        }
        }



    }
}

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The problem is that this form redirects to the first form that must delete the whole folder of pictures and creates a new one (with the same name but with different photos, when the player must repeat the level)...but Visual Studio always throws an exception that the last picture is used by another process and  can't be deleted...Can i fix this in a way that i can still use the picture with its filename (i mean each photo must be shown with its name underneath)?