Hi, I can understand your concern for the recurring bumps under arm pit which is itchy and painful. It appears form your query that you have developing ingrown hair with inflammation at the affected region. This area is quite common to get infected very easily because of sweating and high bacterial proliferation in arm pit area. Do not try to even touch or pinch the area as can cause more aggravation of the problem and spread of the infection. For time being period you can apply antibiotic cream such as fucidin or mupirocin and take pain killer tablets such diclofenac or paracetamol. If it is increasing despite the treatment then meet a dermatologist or any family physician and get a proper treatment without delay for the oral antibiotic such as ciprofloxacin or cefadroxyl 500 mg two times a day for 5 days to prevent secondary infection. Wear cotton clothes and cotton undergarments, take two times bath and stay away form hot and humid climate. Take care.