I have a red bump under my arm its red and hard. hurts to touch or when my shirt or when i move my arm. i was sndrome what it could be.

Possibly...: Folliculitis is an infection in the hair follicles. Each hair on your body grows out of a tiny pouch called a follicle. You can have folliculitis on any part of your body that has hair. It is hard to make a judgement since I am not there to see it, if it continues to bother you i would recommend seeing a dermatologist.

Sounds like abscess: You may have a boil or abscess forming in this area, or this may be a very inflamed lymph node. This should definitely be seen and diagnosed by a medical professional. Go and see somebody and get better soon.

You : Mean armpit? If this is a case you have hidrosadenitis which is an inflammation of sweat glands. Go please and see a doctor as you may need antibiotics or even open it up to drain if on can detect pus. Do not neglect this. Do not use antiperspirants just deodorants as the first could create what you have. Some medical voices claimed that antiperspirants my play a role in causing breast cancer.