I am 55 and 4 years postmenopausal. I too woke with very tender nipple a week ago, and it shows no sign of abating. I also noticed a marked swelling in my labia at the same time, which has also persisted. These 2 things together make me assume there has been some kind of hormonal change, but other than this site I can find no information. Glad to know that I am not alone.