Under my right arm towards my boob but on the rib i feel a lump painful to lay on and tender to touch any ideas what this is?

Lymph node: This sounds like an inflamed lymph node similar to the ones you get in the neck when fighting off an infection in the head or neck.

Lymph node?: It's possible this is an enlarged lymph node. Lymph nodes often become enlarged when that area of the body is fighting off some kind of infection- whether big or small. If you have other symptoms like cough or shortness of breath, this may explain. Also could be a small cyst under the skin that could be evaluated by your doc to see if needs to be excised. Maybe seeing your doc would be appropriate