Small hard ball under my scar where I had a painful intramuscular lipoma removed outside of right rib cage. 5mths post op, right side hurts to touch.

Suture granuloma? If the lump is painful, it likely should be removed. At the scar site, the most likely cause is a chronic inflammation around a buried suture, but since this was at the site of a benign lipoma, a second look at the pathologic diagnosis is warranted.