My question is that when iam 12 I have breast on chest and when iam about 17 my breast has gone down but my nipples is big and worse how to reduce?

Gynecomastia. Breast enlargement is fairly common as boys go through puberty. This is called gynecomastia. As you grow older the breast tissue usually resolves as it did with you. If you do not like the appearance of your nipples you will need to consult a plastic surgeon as there is no medication or treatment to fix this.