Does gingivitis suddenly appear?

I’ve noticed today that my gums are sore under my nose, if you see what I mean. I brush regularly, so I am hoping it’s nothing serious. Also it’s only three front teeth, which seems odd. I was whacked in the face by my dog’s paw a few nights ago, so it’s possible that it’s simply an afteraffect of that incident. Not asking for medical advice for myself so much as if something like this can just suddenly pop up?

Why do biiiiirds…sudddddenly appeaaaar…everytime…you are neaaaaar…