How To Cure Cholasma On Face?

Hello. I developed cholasma on my face a month after delivery. I had a son with natural birth, no epidural and did not take any medications or birth control pills. I exercise regulary and am not overweight. I do not smoke or drink. Please advice as I have my brothers engagement in two weeks. I do not wear makeup as I have always had good skin, please help me get rid of them. Thanks.