Red painless spots on gums&roof of mouth, canker sores on tongue.had a cut in mouth around mth ago before it start happening. cellulitis?oral allergy?

Red spots tongue, so: Can be allergy (is it worse after eating something?) or strep or autoimmune manifestation. With red painless spots we also consider low platelets so would follow up with doctor or the ER today.

Red spots: How long have they been there. If longer than 2 weeks get them checked. Lots of possibilities, the vast majority benign. Very small percentage problematic. So if they don't clear in 2 weeks from onset, knee your General Dentist.