Temporary puffiness?

[skeptical]

My right nipple looks totally fine all the time (to me at least), but the left one sometimes looks puffy and other times looks identical to the right nipple. Generally, it seems puffier in warmer temperatures.

Could this be related to gynecomastia or is it something that all men experience

[aleksandar]

It's impossible to know for sure from description only, but it could be unilateral gynecomastia. Unilateral means one side only. It's not quite as common as bilateral, but it's not unusual. Unlike fat - if it were fat that makes your nipple puffy, it would be distributed equally left and right. It's the natural law.