For the past two- three months my right upper arm has ached and been sore.  It hurts to even take off a shirt or to scratch my back.  I thought maybe was sleeping on it wrong, so changed sides but still no relief.  This morning my husband noticed a lump on the outside of my right upper arm that is under the skin.
Hi and welcome to Chat Doctor. It is hard to say, but it sounds like swollen lymph node or some subcutaneous lesion, and you should do ultrasound to verify this and plan further treatment. . Wish you good health.