Hi there Amal Nair
I apologise for answering as this query seems to be directed at Dr Grief but sadly on a public forum, it is not requisite for us to answer & at times we may not even know until & unless the moderator directs the query to the particular doctor, so if you permit me, shall make an attempt to answer your query.
The best case scenario for you in the situation you described would be to apply a good quality sunscreen with an SPF of at least 20-30 assuming you have an Asian skin type; This will have to be applied & stay on your skin from dawn to dusk & reappiled ideally each 3-4 hrs & in sufficient quantities.
Moreover, if the face/hands are washed, sweating or swimming, then it has to be reappiled & it ideally has to be applied at least 20 mts before sun exposure.
There are various brands of sunscreens in India & one will have to choose based on individual aesthetic senses & the cost factor. My personal favourite is an international brand from a company called Bioderma that is now available in India. They have tinted & non-tinted varities & for your case a particular brand called 'Spot cream' or lotion that contains a built in pigment lightening agent ;-)
Cheers & Good Luck & wish you a radiant skin!
Dr Praveen Rodrigues MD
, Cosmetologist, Venereologist
Vikram Hospital, Bangalore, India.