prednisone 40mg two days

I'm 33 female I was on 40mg of prednisone for 2 days for an allergic reaction to bactrim. I didn't get either prescription from my pcp but an urgent care. Will this compromise my immune system and for how long? I always thought you had to ween off steroids as well? I called my dr but they haven't returned my call due to the holidays. I'm going to try to call the pharmacy today but please let me know your experience with either bactrim or prednisone.