I am relatively new to using meth IV, and yesterday I had a friend help me by injecting the drug for me. The needle was new & never used, blood registered in the syringe when she pulled the plunger back. She stopped when I felt stinging and checked to make sure she was in the vein, and she was. Very mild stinging continued for the last 7 to 8 units of the shot. I immediately started hot compresses and massaged the area, and when no knot came up I thought it would be fine. This morning I woke up and my forearm has a large swollen knot and bruise. What caused this and what can I do to relieve the swelling, bruising, and tenderness?