Hi LeslieWright and welcome to ehealth: If you are talking about something the size of a large pore then I know what you mean...It is on the nipple itself..Every once in a while I will still get them and they act exactly like yours do...At first I wondered if they were pus, but like you stated they are just thick and when you put pressure on it from both sides it expels...Funny thing about this is that I didn't breast feed any of my children...
I really wouldn't worry...However, the next time you go to the doctor ask him/her what causes this...If I think of it I will also ask mine who I will be seeing next month...Take care...
Caroline
****Added....I just read the two previous posts above yours and they explain what they are...Now, we both know....