I've found a soft lump on my back. it's approx 2 inches below and 2 inches across from my armpit. it's on my rib cage. it's also painless.

Lipoma: The most likely diagnosis is a lipoma. A lipoma is soft and mobile. If it seems fixed to underlying tissues then many other diagnoses become concerning. It's best to see a local orthopedist, general surgeon or dermatologist. They should all understand this lesion.

Lump: If the lump is on your back, i would think it is a cyst of some kind. If it is mobile (meaning you can move it side to side, up and down) and it's been there for a while unchanged, it sounds like a cyst, probably sebacious (oil gland clogged). I would see a doc to confirm it, though, and have peace of mind.