i had a lump a year ago which went, but it left my nipple kinda sagging over it's self a little and it hasn't gone back to normal and now I have an even bigger one in my other nipple. it happened after a nipple twister :/ and I'm really self consious about them both and always have to wear a jacket just to cover them up
It's completely normal. It may sound wierd but if you run them with water it will actually make them smaller. (Not Trolling, Completely Serious)
i have lumps under mine to and im 15, i've had them since i was 11, they always go and come back, and when i put pressure on them it hurts, but the lump i have now has been there for a year and a half, in my left nipple and keeps getting gradually bigger and bigger, but after a lot of research its just puberty and it will go so basically there is nothing to worry about. But if you want to double check its easy to visit a doctor etc.