After a strenuous workout, etcc...next day i noticed bump on armpit. it's painful when touched, not red. sweat gland, boil or lymph node? i did not wear deodorant during workouts.

It could be: Any of the three you mentioned but most likely folliculitis. The gland at the root of the hair is clogged and is not able to express the secretion and swell up and get infected. You may need antibiotics and warm compress. Your doctor should be able to tell you when he sees it. Good luck.

Sounds like: An infection. Show it to a doctor, so he can treat it properly.