For the place you mentioned, it's a must to use sunscreen of spf 30 twice daily, even if indoors. Tanning occurs due to cumulative sun exposure and UV Rays from other light sources too
Next Steps
1. A sunscreen gel of SPF 30 minimum, twice daily, in morning and afternoon
2. A cream containing Kojic Acid and
Vitamin C, like CLEARZ PLUS(by Dr.Reddy's) at night
3. Visit a dermatologist in your vicinity for chemical peels, if tanning is very severe
Health Tips
Hope there has been no use of any steroid creams over the counter or from friends recommendations