‘Already Installed’ error after updating core

Had a message in my admin to update core; updated and now I get the ‘Already Installed’ Error telling me to clear old database tables first. I do not want to clear my old database tables as I wasn’t trying to reinstall; I just wanted to update. Now, I cannot access my admin area because I keep getting redirected to this error screen and it tells me to login. Is there a way to clear this message so I can get into the admin, or is there a way to salvage my data so I can backup the database and port it to a new install? I’m not sure why this has happened w/ a fairly normal update?