What is this on my nipple?? 😣

I’ve had this bump for YEARS. Like maybe 10 years. It’s never gotten any bigger or smaller, and it doesn’t hurt. There’s nothing “underneath” it from what I can tell, it just feels like a tiny mass of hard tissue. I thought it was a clogged sebaceous gland and I’ve tried to squeeze it and nothing ever comes out. Then I thought maybe it was a third nipple because it gets harder when it’s cold, but it’s not on the nipple line where extra nipples are usually found.

I’ve never been pregnant or breastfeeding in my life.