urgent – messed up my WP site real bad

I went into the “Options” tag and put the wrong URL in for the site I’m working on. In short, I’m creating a site on a staging server, and wanted to set the URL to the URL that this WordPress site will eventually be moved to. Now, it has permanently changed the address of the WordPress blog to that URL, and redirects everything (even mysite.com/wp-admin) to it. There is no way I can even get into the admin panel anymore…what do I do?