Click the lock to make changes button won't work

Hi!

I wanted to change administrator user name, so i did. Computer restarted, but after going in User & Groups user name was the same as previously and "click the lock to make changes" button won't work, because it doesn't support none of the user names or passwords - old or new ones.

Basiclly, now I can't get admins access to my computer, because it's locked!

Please help me!!!?