I have a small red bump under armpit (right) the bump is slightly to the right and it is sore. is it a bad sign?

Small infection: The description is likely a small boil. A boil is an infection of a hair follicle, usually due to a Staph bacteria. In the center is a small collection of pus. The boil may resolve on its own or get larger and burst draining pus. Warm compresses may help bring it to a head. If it continues to enlarge see a physician who can drain the abscess. See http://bit.ly/1Hi4wm1

Armpit bump: sound like infected hair follicle. se your gP for review and possibly antibiotics.