A Couple Days Ago I Shot Up Heroin Into My

A couple days ago I shot up heroin into my right arm. I noticed the day after that it was numb and hurt. It has been gettin worse and my arm is numb from the crease of where the arm bends (also where I shot up) almost all the way down to my wrist. There is also a slight burning feeling and it is very painful to touch and to move my arm, especially when I extend it out all the way. It is also warm to the touch. I am very worried about it and am wondering if it is really serious and what I should do about it. Please help.