Changed URL in settings, DNS address not found

Hey so I’m super new to all of this site building stuff. I made a stupid mistake of changing my wordpress and site URL without changing/buying that new URL from my host. Now, whenever attempting to access my site I get rerouted to a page saying my “server DNS address could not be found.” Any attempt to change the URL’s back to what they were has been futile. I keep getting that page and now I’m completely locked out of the site.