I IVd Coke A Couple Days Ago. And 4-5 Hours

I IVd Coke a couple days ago. And 4-5 hours after something popped in my arm and 1/4 of it turned red hot and swollen. That was on Tuesday now it doesn't hurt so much but the swelling redness and heat has almost traveled all the way to my wrist and there's a huge knot in the crook of my elbow. What do I do? And what could have happened