Nipple size, shape, color and whether they are flat, inverted or erect vary from guy to guy and woman to woman. Basically, no two nipples are exactly the same even if they are on the same body. All of the different types of nipples are usually normal unless your nipples suddenly change from being straight and erect all the time, to being inverted (flat and pointed inward instead of out). It’s important to know that neither exercise nor sports will change the appearance of your nipples. It’s a good idea to mention your concerns to your primary care provider (PCP). He or she will examine you to make sure you don’t have anything to be worried about. Although it is rare, adult males can get breast cancer so if you notice any usual symptoms, such as blood from your nipple, make an appointment with your PCP right away. If having flat nipples is causing you emotional distress, you might want to talk to your PCP about cosmetic surgery or injections that may help make your nipples straight and erect, but cosmetic surgery is usually not covered by most health insurance and is an out-of-pocket expense and comes with risks.