White sore on my lip?

I woke up this morning with a white sore on my lip. It's raised and feels kinda like a canker sore, although not as sensitive, at least at this point. Does anyone know what this is? My only guess is a canker sore but I've never had one on the outside of my lip before. I don't think it could be , seeing as how I'm still waiting for my first kiss and rarely even share drinks with people. My lips felt dry last night and I got pretty sunburned 3 days ago. Thoughts?