It seem that your has developed sun burn and excessive tanning
after sun exposure. Do not apply any home remedies
which can aggravate the situation. You can apply cortisone
cream and calamine
lotion over affected area.
Use a good quality medicated sunscreen 3 times a day. Protection from direct sunlight is must . Do not apply any cometics which are containing fragrance in it as it can also cause pigmentation on exposure to sun light.