I have "ball" growing inside my right armpit. i can also feel it as a bump when my armpit is open. should i be concerned?

Tough : There are a number of possibilities that could cause what you describe, which includes a cyst, lymph node, fatty tissue (benign), etc. The most common causes, however, are not worrisome. The best way to know for sure is to have a doctor do an exam and possibly some imaging depending on their thoughts from examination. Make an appointment to see your primary doctor ASAP. Best wishes.