Apple ID password restoring

Dear All,

My son's phone (Iphone 7) started glitching and I had to reset the phone completely as it just couldn't turn on (there was just Appl log on the screen all the time). Once they reset the phone it asked me to log in and I could not remember his password. I tried several times and it was wrong, so they blocked any further attempts. They said they are going to send the instructions to his email, but I don't have access to it as his email was available only on his phone. Not the said - the next time you can restore your password is in 13 days!

Please, guide me through and help to unblock his phone.

I have his Apple ID in my Family list on my own Iphone.

Thanks

Valerii.