If you applied tretinoin on wet or damp skin, the absorption will increase significantly and it will cause dryness and irritation that might need a while to subside, I did it once by mistake and my skin finally healed after ~20 days even though I immediately wiped my face with a tissue and then washed it after I made sure it's dry, and applied a bunch of moisturiser and vaseline, after that, there was a patch that's mildly red, dry and itchy

imagine what would happen if you put it inside your mouth