in that area. You should consult a dermatologist and get prescribed various skin creams like hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser treatment. If it still persists then you can go in for laser treatment, Chemical peeling or microdermabrasion. Also then the possibility of acanthosis nigricans has to be ruled out.
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.