Whitehead Directly on Bottom Lip

Patient: I have had a white head.(not a cold sore. I’ve never had a cold sore before. Looks kind of like a canker sore/zit) come up twice directly on my bottom lip about the same spot when I go a couple of days without chap stick. Once it appears and I pop it, it goes away. There is nothing there. Just a little sore the next day. What could this be?