Nipplescan be awkward, to say the least.
What makes them do this?
Why can’t they just stay flat?

One of the most common times nipples get hard is when you’re cold.
This tightness then pushes out the nipple, and hence, cold weather gives you hard nipples."
That seems straightforward enough, but what about the other times that our nipples get hard?
The nerves in your nipples react to physical and psychological stimuli, saysHealthline.
Some people have more sensitive nipples than others and will find that their nipples harden more easily.
Things that can make your nipples harden include arousal, pregnancy, ovulation, breastfeeding, and even allergies.
Nipples can even harden at random, and there’s just no explanation for what’s going on.
Most of the time, your nipples getting hard is a totally normal occurrence and nothing to worry about.