My 9yr old set his laptop up with his dad. I wasn’t there. There is no email address linked. Idk what to do

My son downloaded Minecraft on his laptop. After a few minutes of playing the entire thing froze. Nothing would change so I put it to restart. Now it restarted and on this screen is only the name and password option with Touch ID. His finger doesn’t matter unless he has the name and password combo correct and since he doesn’t remember. I am not sure how to get this laptop back up and running