is this cancer?

i have a pretty big bump(???) underneath my skin right above my ribs on the left. it looks like im growing another boob. its soft, and it moves when i poke at it. the only time it hurts is when i continuously mess around with it, or if my bra is digging into it. its bigger than 3cm, and google says its cancer. im only 15, and super stressed about this. my friend said its probably a fat deposit but google says fat deposits are no bigger than 3cm. would it be hard and painful if it were cancer? i want to get it checked out but im super hesitant.

Hi
Is the lump above the clavicle or below?Lipomas (fat deposits) can be any size.

its below it! underneath my breast, but not touching it.

let me rephrase that, haha. its below my breast, on top of my ribs.

It could also be a sebaceous cyst , don’t wait ,go to a Dermatologist so you’ll stop worrying.