Does it just hurt to touch or even when nothing is touching it? Have you tried physical therapy? My armpit is like one big knot. It doesn't bother me anymore, but I've gone through PT for a couple months 3 different times to work out painful knots that were in the lymph system. It never brought that area back to normal, but it really did help and get rid of some if it. Only the side that had lymph nodes taken out has knot issues, but range of motion was affected on both sides. The PT really improved my range of motion as well. If I do any heavy housework like hard scrubbing the knot gets bigger. I hope PT might help you.