administrator name

See some articles If you forgot your user or account name on your Mac - Apple Support

And if you are unable to login in see these Change or reset the password of a macOS user account - Apple Support

If you need to update your keychain password on Mac - Apple Support

Can you log in?

If so, System Preferences > Users & Groups

All user name will be listed in the sidebar.

Let us clarify this.

System is not accepting your administrator name?

You cannot open the the Users & Groups pane?

Administrator account became standard and you don't have an administrator account?