hot nip
When your nipple is not erect, looks puffy in appearance and is spongy to touch. Often happens when you have just woken up in a centrally heated house or sunbathing.
For example;

Man: Ergh.... babes..... Wtf is going on with your tits? Why do they look all flabby and weird??

Girl: babes, I've just woke up? It's only hot nip..... Give em a pinch?