Does something like "cooties" exist?

I have a sore on the corner of my mouth but I don't think it's a cold sore. I got this once before when I was little, and I just called it cooties. When it dries out it just looks like crums on my mouth but if I pick it off it comes back bigger and more painful. When it's wet, it looks like I can just wipe it off. I've only had it for a couple days. If I try to look up cooties I don't find anything and I don't know what else it's called. What is it? This is only the second time in my life I've gotten this.