B.P.
I'd give it a few days. Bactrim is the standard med for staph infection, but like the other poster said, it will take a few days to work if they didn't start you off with a shot.
Do go back if it gets worse or isn't better after 48 hrs of taking your medicine as directed.
Try to relax as well. Staph infections aren't nearly as "scary" as they used to be. Sadly, they are quite common and are easily treated.