Rash on trunk-haven't taken anything unusual

Hello there, I am a man who is 42 years old. Long time ago, I was bitten by some insect. I wasn't looking and therefore I didn't know what bit me. This spot became infected and I had problems with a rash on trunk. I had to take erythromycin for some time and the results were good. That was couple of years ago. Lately I haven't taken anything unusual, except that a week ago I had to get a shot of steroid in my knee. Now the rash is back and I don't know what it is.

This sounds like a long shot, but I had similar problem. I was diagnosed with Lyme disease. You have to go to doctor because this is a tough thing to diagnose. Maybe that steroid shot might have caused Lyme disease to activate. But that insect that bit you surely could be a carrier of the disease.