Soft fibroma https://en.wikipedia.org/wiki/Skin_tag
Soft fibroma is a soft nodule that most commonly appears on the neck, armpits, or groin.

More information ― English
References A soft fibroma of the nipple - Case reports 36276909 
NIH
Although soft fibromas occur in the intertriginous area, including on the neck, axillae, and vulvovaginal locations, in rare cases, they can develop in the nipple. Doctors should consider soft fibroma as one of the differential diagnoses for nipple lesions.