Dashboard problems

HI,
I have big problem. I just make some changes on my dashboard for mistake, and now cannot access to my account and my site have no theme at all.

I just went to Setting, General, and change one letter from my site address. Now my site is not working and I cannot access to my wordpress account. Please can any body help me? How can I access to Dashboard again and go Setting General to make it right again?

Thank you