could be herpies simplex. see your doctor or even your dentist.
Could be a cold sore, they can be white. also, could be an allergy to something you may have eaten. I would see the dentist, he will be able to determine what it is.
Get in to see your Dr. These does not sound like cold sores because they're usually red. Are you in the sun a lot, did you eat something you normally don't? Be safe and have your Dr take a look at these. Remar