I have a small lump under armpit and its been there since last 2 months.it pains sometimes.what can be the reason and should i be worried?

Cyst? Lymph node? : Likely a cyst or lymph node. If it's tender, it may be inflamed, & so will need to be checked if tenderness doesn't improve in 3 days, in case you need antibiotics. Anyone in your family ever have similar symptoms or a condition called "hidradenitis"? If so, more likely that's what you have. Do apply warm compresses to area in the meantime. Hope that helps.

Exam: You may have an inflamed or infected lymph node in the axillary (armpit) area. You must be seen and examined.