Suggest Treatment For Lump Between Shoulder And Neck

I have a hard lump between my shoulder and neck on the right side. It s been there for about three weeks now; it doesn t move around or relax like a muscle knot when I use heat, massage, or IcyHot. The shoulder, shoulder blade, and entire arm are very painful. I have swelling from the shoulder all the way down to my fingers. Ice seems to actually make it worse; heat and anti-inflammatories help a little. I have very limited movement and am starting to get sharp stabby pains in my upper arm.