i have just injected heroin into a vein on my forearm, midway through I felt sudden burning at the injection site and then all the way up my arm to my hand which cramped up. I immediately stopped at this point. The vein I was using visibly swelled up briefly and ran noticeably down to the area of my hand which was cramping. All along my arm has swollen and developed red like rash whilst my fingers have also swollen but turned white and are stiff to move now. There is no physical pain now but due to fingers swollen it is hard to close hand to make a fist. What should I do? Should I be worried? My assumption is that have missed the vein or somehow hit an artery and have had an allergic reaction to the citric acid which has caused the rash and swelling of arm