Bump on nipple? TMI WARNING

‼️ TMI PHOTO WARNING ‼️

I recently got a swollen bump on my nipple. It was hurting very bad one day and then when I looked I saw this. It’s only been 2 days and it’s starting to go away and the pain is no longer there but the bump is.

Idk if this is normal? I’ve had this before a while ago and it went away completely but I was told it could because I don’t clean it enough or my bra is too tight or it’s irritated. I don’t know but I’m kinda curious if this is normal or serious.

My left arm has also been hurting a little bit, not sure if this relates to this bump but I just get scared of the worst case scenario. I’m barely 21.