entered wrong domain in settings and can no longer log in to admin

I had a domain name pointed to my DNS and I was trying to mask the current url to reflect the name of the new domain. I added the new domain url into the setting area where it asks for the url, changing the original url. The site is still running, but I am unable to log in to get to the dashboard to change the link back. Also, is there actually a way to mask (don’t know if I’m using the correct term??) the current url to the new url?