Is it showing any email address at the login screen?
What does it shows at the login screen?
Does it shows the username above the password ***** or a back arrow to go back?
It seems like it is a local account that has been setup, if it was a microsoft account (if it showed your email address) then we could have resetted it easily, but since it is not you will need to reset the PC and set the account again. I hope there is nothing important on the system. To reset, you need to hold the shift key, and whilst still holding it click the Power icon on the lower right corner, and choose Restart. Once it restarts, choose Troubleshoot -> Reset this PC and follow the prompts on screen to fully reset the system. After the reset, you will be able to set it up again like new.
Will take 30 mins to 1 hour.