You're probably going to have to factory reset the phone. Google your phone type and the words factory reset. It usually involves powering off the phone and then starting back it up while holding both volume buttons then choosing the reset option.
WARNING: YOU WILL LOSE EVERYTHING ON THE PHONE.
I hope you are backing up to the Cloud, if there is stuff you wanted to keep.
Enter random password how many times you can and should asked if you forgot password and it will ask you to sign in using your Google account