Sometimes nipple tips are flat or even point in, rather than pointing out. This is called inverse nipples. If it doesn't bother you, it's not a problem and you can ignore it. It won't affect nipple piercing, breast feeding, etc... However, if it does bother you, you can alter your nipples!
Nipple piercing is the easiest thing to do in most cases. The piercer simply "pops out" the nipple and pierces it normally. Generally the jewelry will keep the nipple in an erect position, thereby correcting the nipple's appearance:
Nipple Pumping (as in vacuum pumping) is another method that can address inverted nipples. Pumping the nipple both enlarges it and coaches it to a more standard form. This is a good approach for people who don't want a piercing, and don't want to try surgical intervention. Suction from syringes can work, as can things like snakebite kits. This has the added benefit of adding sensation as well.