@GreRobs: that's not a meta keyword you added; you changed the URL of the site. The URL has nothing to do with site meta and SEO.
You don't necessarily need to restore a backup.
Every once in a while, somebody finds a need to manually change (or fix) these settings. Usually this happens when they change one or both and discover that their site no longer works properly. This can leave the user with no easily discoverable way to correct the problem. This article (linked below) tells you how to change these settings directly.
See Changing The Site URL « WordPress Codex for recovery instructions.