My mouth in general isn't sore, and my tongue is fine, so I don't think it could be either of those.
I'm having a flare-up of my eczema/dermatitis (which is in part caused by contact allergies, but I haven't a clue what has triggered it) and am getting lots of little almost-ulcers on my gums, and sore, slightly rough, patches inside my cheeks and just inside my lips. All on one side of my mouth, the same side as the flare-up on my face. Hence why I wondered whether they were the same thing.