Hello,
From the symptom that these are itchy and painful bumps rather than a rash, it can be due to folliculitis or shingles. Folliculitis is the inflammation of one or more hair follicles. The condition may occur anywhere on the skin.
Folliculitis 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 (staph). Shingles occurs in people who have had chickenpox and represents a reactivation of the dormant varicella-zoster virus. The first sign is usually a tingling feeling, itchiness, or stabbing pain on the skin. After a few days, a rash appears as a band or patch of raised dots on the side of the trunk or face. The rash develops into small, fluid-filled blisters which begin to dry out and crust over within several days. When the rash is at its peak, symptoms can range from mild itching to extreme and intense pain.
To confirm the diagnosis please get it evaluated from a dermatologist.
I hope it helps. Take care and regards.
Try over the counter anti fungal cream located with the feminine hygiene products in most stores.