What Causes Puffy Nipples?

Hey I'm a 17year old girl and ever since I started growing breasts my nipples have been puffy and I just want to get did of them. They only go smaller and hard when there cold but I prefer them like that because it makes my breast more rounder because when my nipples are puffy it makes my boobs are more pointy. Is there anything I can do? Will getting my nipples pierced help? Please help me they really bring me down!