Thanks everyone for the input! I took a damp q-tip and gently rubbed at his lip and he popped his mouth open for me on his own; it wasn’t substrate as he’s kept on paper towel but whatever it is it isn’t mouth rot and some of it flaked off on he q tip, so it’s either a very minor scab or a little bit of dried on pooI will definitely keep an eye out for swelling or irritation but it seems like he’s just fine and I really was just being an overly paranoid dad
Thank you all so much!