Why did my face turn darker after chemical peel?

my face turn darker after i did light chemical peel which was 3 days ago. Is it one side effect? How many days it will take to turn to my normal skin colour? My skin has been peeling a little bit around my mouth and nose(like powder). I still feel tight around my cheeks,nose and mouth. The doctor give me a recovery cream for this 1 week period(morning,night). He also give lightener cream which is to wear after 1 week (night only). I wear sunscreen 60spf, i wear it even when im in the house.