Changed URL, now I cant get into site

Earlier today I was wondering around on my site and changes the site url to another site I own, but now I cannot log on as administrator of the site anymore! I looked at all the feedback for this problem other people have had, but I don’t know how to even access mysql wordpress or what that even is! I am so confused. It is imparative that I get this site back so I can change some things! If someone could please tell me in a direct manner what this all is, I would be very appreciative!

I do not know which version of wordpress I have.