Suggest Remedy For Raw And Reddish Shaft Skin Along With Yellow Coating

I saw my urologist for a prostate issue (infection) and he prescribed bactrim for three weeks. I had what the ER doctor called an allergic reaction to the antibiotic, but I scratched my entire groin area raw, specifically the areas between my legs and testicles and the shaft itself. The areas between my legs seems to be healing- still a bit raw, been treating with prednisone steroid pill and desitin like diaper rash- but my penis shaft is essentially hiding. When I try to extend it, I can see it is very raw and red and there is a milky yellow coating to it. It is very painful when I try to urinate. How should I treat the shaft to get it to heal?