I'm a 20 year old female, and have noticed a hard, painless pea-sized lump in my armpit. it's been there for two years or so now, what should i do?

Lump: What you describe does not sound to be dangerous, not anything like cancer, since it has been asymptomatic and stable for 2 years. If you want to have it removed you can see a general surgeon or a family physician, most of whom are able to do simple excisions. The doctor may then advise to send it for a pathology report to know specifically what it is.