Without examination,confirmation of a diagnosis is tough but it can be contact dermatitis, rash due to friction rub,folliculitis,cyst ,molluscum contagiosum(multiple, small, dome-shaped papules, often with a central depression or plug) or some benign skin growth.
Apply warm compresses, Neosporin ointment and calamine lotion and avoid messing with it. You can take anti-inflammatory pain killers like ibuprofen or acetaminophen. If the lump persists then it will be best to get it evaluated from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.