I Have A Slight Bulge On My Left Side. When

I have a slight bulge on my left side. When I feel in that area, there is a lump that feels hard and oval. I have noticed it at night when I lay on my left side, but today after showering, I could see a distinct difference between my two sides. I also noticed today I feel a twinge in my back. I have been on Penicillin since Friday for a tooth abscess.