Hi,
Without examination, confirmation of a diagnosis is difficult, but it seems like folliculitis or a boil. Folliculitis is the inflammation of one or more hair follicles. The condition may occur anywhere on the skin. It starts when hair follicles are damaged by friction from clothing or blockage of the follicle. In most cases of folliculitis, the damaged follicles are then infected with the bacteria Staphylococcus.
A Boil is caused by an infection of the hair follicle by staph aureus. Bacterial skin infections can be spread by shared cosmetics or washcloths, close human contact, or by contact with pus from a boil or carbuncle.
Apply warm compresses on the bump and keep the area clean. You should consult a doctor as you might need a course of antibiotics/anti-inflammatories to take care of the same.
I sincerely hope that helps. Take care.