Do you shave your armpits for hair removal? If so, the bumps could be ingrown hairs, especially if they’re large and uncomfortable. Nads make a really good ingrown hair solution that will calm down the hair follicles and skin.
And if you do shave, I’d suggest looking at other types of hair removal like hair removal creams and gels – they completely eliminate ingrown hair issues usually. I know because I usually use creams, and through using a razor instead last year, I ended up with a horrid ingrown hair issue. It resolved easily for me with the Nads ingrown hair gel, and swapping back to hair removal creams