Hi, I can understand your concern for the itching bump on the inside of your right butt cheek. There are two possibilities of your problem: 1. Ingrown hair or folliculitis 2. Sentinel Pile with infection in the same. It appears form your query that you have developed infection in the area with inflammation at the affected region. This area is quite common to get infected very easily because of sweating and high bacterial proliferation. For time being period you can apply antibiotic cream such as fucidin or mupirocin and take pain killer tablets such diclofenac or paracetamol. Do not try to even touch or pinch the area as can cause more aggravation of the problem and spread of the infection. If it is increasing despite the treatment then meet a surgeon or dermatologist or any family physician and get a proper treatment without delay for the oral antibiotic therapy to prevent secondary infection. Take care.