you need to be seen today or tomorrow and get a proper exam done. this could be many things and I agree that it could be a bacterial skin infection that needs proper treatment.
have you sought out treatment for your drug issues too?
grace
Since you were using IV drugs.....you could be having an abscess. When you were using the IV drugs, did you muscle your drugs. They call it skin popping. It's when the user injects the drugs into a muscle instead of the vein. When people do this they really run a very high risk of getting an abscess. You need to seek medical help. You could end up with Staff infection or worse. You will probably need some antibiotics.