Mouth ulcers. I suffer from those on a regular basis, most often when my immune system is a bit low. They can be painful as all hell. Accidentally touching them with the toothbrush can be tear-inducingly painful. I winced upon realizing what Sukuna was doing here.
getting a mouth ulcer is so annoying. it can sometimes last a week or 2 and usually makes me not want to eat or unable to enjoy what i do eat due to the pain. had a few times where i just had to bite the damn thing off. hurt like hell, believe me, but that intense pain followed by days of relief is worth it....aside from all the blood and other liquids from the initial removal.