Sounds like maybe you Migrated from the MacBook Pro after you setup Mac Mini.
If you did that, then now have two User Accounts on the Mac Mini. The new one that you initially setup and the old one that you Migrated from the MacBook Pro.
If that is the case and you want one account, then you need to decide which User you want to keep. Then manually move the /Users/Shared Folder Files from the unwanted account to the /Users/Shared Folder of the wanted account, then delete the unwanted User account.
An second option, is to just live with two User Accounts on the Mac Mini.
A third option involves wiping the Mac Mini and starting over.