Hello dear patient, this is completely normal unless you have pain. Shrinking with cold response is normal for these body parts. Don't worry.

In case of excessive sweating with repeated rubbing of the nipple by the clothes you're wearing can cause irritation of the nipple. A few steps which could be of help are: - Avoid excessive sweating - Wear an inner vest and wear loose comfort clothes which are soft on your skin - Avoid touching it repeatedly and apply ice over it to bring down the inflammation. If the problem persists or worsens visit a dermatologist