Cold sores: is it possible for them to just appear?

I have a bump on my lower lip that looks like a bug bite. I thought it could possibly be a cold sore but it doesn't itch. It's just red. Barely noticeable. But could it be a cold sore and could it just appear out of nowhere? I haven't had interaction with a guy in awhile too. So I'm confused as to how I could have even gotten it😕