Small lumps under armpits for yrs; some slightly protrude. i once nicked one and thick yellow came out. biggest one is smaller than a pea. no pain.

Maybe: Hidradenitis Suppurativa. It can involve the glands of the axilla. Be examined. There is treatment with antibiotics and antibacterial soaps. Severe cases are often referred to surgery. All the best.

Cysts: These are probably epidermoid inclusion cysts. Best left alone.

Hidradenitis?: This sounds like hidradenitis suppurativa, a chronic inflammatory condition of unknown cause that often affects the armpits or groin, sometimes other areas. It can be serious and often treatment with antibiotics is needed when the area becomes infected, which is qute common. See a doctor, preferably a dermatologist. Good luck!