by staph aureus.Hair follicles that are blocked by greasy creams, petroleum jelly, or similar products are more vulnerable to infection. Bacterial skin infections can be spread by shared cosmetics or washcloths, close human contact, or by contact with pus from a boil or carbuncle.In your case,it could have been due to blockage of the hair follicles.
Pls keep the area clean and apply some warm compresses. Also wear loose-fitting cotton clothing and use an antibacterial soap or mild soap like dove.Avoid any kind of cosmetics. Topical antibiotics such as mupirocin or neomycin containing ointment are also useful.In case the symptoms persist then oral antibiotics may be needed.Then you have to consult a dermatologist as they are available only on prescription.
Hope it helps.Take care and pls do keep me posted if you have any additional queries.