Large Pimple Under Armpit. First and foremost good underarm hygiene is essential to help get rid of armpit pimples and prevent them. There are many medical reasons that can result in underarm pimples that are painful.

Read below for more causes and treatments options. There are many medical reasons that can result in underarm pimples that are painful. A small or pea-sized lump in the armpit can also be caused by a skin infection like a cyst or ingrown hair.
So be prepared for that.
You may be wondering whether the bump in your skin under your arm is a boil or a pimple. For those who dont shave their underarms but experience armpit bumps that are hard like a marble. Apply the compress to the cyst and hold in on your armpit for 20-30 minutes. This condition can also be associated with tenderness or pain in the lump under the arm.