Thanks for writing to us.
Most probably you have developed sun tanning over face. Sun damage is maximum during 11 am to 3 pm sun exposure.
To treat the same
Use a sunscreen with SPF 30 half an hour prior to going out in sun.
Take vitamin c supplement
like celin 500 mg twice in a day
Apply a hydroquinone
based cream in minimal amounts in night.
Taking few sessions of chemical peels
would help you immensely. For the same consult a dermatologist
Hope that helped.