It seem that you have developed the condition known as Pseudo acanthosis nigricans
. It is a common condition mainly seen in bit overweight
persons. Do not apply any home remedies
which can aggravate the situation. You can apply creams such as Azelaic acid, glycolic acid
and kojic acid
can be used to reduce the pigmentation under dermatological supervision.
You can also go for latest treatment including chemical peeling under dermatological supervision. Use a good quality medicated sunscreen 3 times a day. Protect yourself from direct sunlight and stay in cold
places to avoid sweating. Do some measures to reduce your weight!!!