For your info
Inverted nipples
Most women�s nipples protrude (stick out) about 5�10 mm. Usually they become about 10 mm longer and 2�3 mm wider during sexual arousal. Some women have nipples that are flat, but become erect during sexual arousal or when a baby is sucking on the nipple. Nipples that are tucked into the breast, instead of being flat or sticking out, are called inverted nipples. Both nipples may be inverted, or just one.
Nipples that have always been inverted. If your nipples have been inverted for as long as you can remember, it is nothing to worry about. It is just the way you are, and a lot of women are the same. A survey of 3000 women attending an antenatal clinic found that 10% had inverted nipples.
A nipple that suddenly becomes inverted can be a sign of a cancer underneath it, so you should see your doctor straight away.
http://www.motheringfromtheheart.com/inverted% 20nipples.html