Hi, I am Dave, I will help you with this.
When you use the Lock option to remotely lock your device on the 'Find my Device' web page, the only option to get back into Windows is to reset Windows, you will not be able to log into the PC normally, usually you will see a notification that an Administrator needs to unlock the device, even though you are the administrator.
Click the power button on the Login screen.
Press the Shift Key and click Restart
Your PC will boot into the Windows Recovery Environment
Go to Troubleshoot - Advanced Options - Reset this PC
Choose to keep your files and apps.
Then start the Reset