Suggest Treatment For Red Lump On Right Arm

I have a large red lump on my right arm. just above and outside of the crook of my elbow. It doesn t hurt, when i squeeze it gently it starts to hurt or feel strange really, around it. But not the lump itself. I am a former IV drug user. But I haven t used a needle in well over three years. Also i don t think I ever used this particular spot. It s not where I would think a vein was located. Can you give me an idea?