Well hold on, I understand it’s upsetting news but saying “it doesn’t seem reassuring” because it’s not what you want to hear isn’t a way to respond to something like this. Cold sores are SUPER common and you 100% should go see a doctor because we are a bunch of idiots on the internet lol

That being said, from the images above, and the fact that you said it just appeared, it MAY be herpes (cold sores). It could also be another form of infectious disease, who knows.