I used to shoot up, (last time was about 6-7 months ago). Now I have a sort of rash in that spot on my arm. Every once in awhile, I'll experience a sharp stabbing pain there, and occasionally a little numbness. I'm not sure if one has to do with the other or not. I was just wondering if the cause was because of shooting up, or something completely different. If it helps, I used to shoot up pain medication and meth. Please help!