Can't access wp-admin — accidentally changed URL under settings

Hi all,

I’m running MAMP on Mac OS and I finally got everything in order and installed a few custom themes. I went to the settings page and I thought changing the URL there would change my site URL, so I just entered a wordpress URL. Turns out though that now everytime I try to access localhost/wordpress/wp-admin, it redirects me straight to the wordpress URL that I indicated in settings (and it turns out that this is someone else’s blog), prompting me for a login, i.e. when I try to access localhost/wordpress/wp-admin, it redirects me to [wordpress URL I entered in settings]/wp-admin, which is someone else’s blog entirely. I just want to reset the URL I entered so I can access my own wp-admin page again

The login I created when installing wordpress doesn’t work though, and I’m at a complete loss for what to do.

Any help would be greatly appreciated.

–Justin