I've gotten leukoplakia before from chewing my lip/cheek. Doc told me it's most often caused when the mucus membrane is irritated by something. In my case I just had to break myself from the habit of chewing the inside of my cheek and lip. Cleared up in about two weeks once I stopped. You don't happen to chew the inside of your mouth do you?

I will cross my fingers for you that your's is as simple and clears up quickly.