Thanks for your query. I have gone through your query. The mouth ulcers can be a apthous ulcer secondary to stress or anxiety. You can take topical analgesic like choline salicylate and topical anesthetic like lignocaine. The swelling in the mouth can be because of the tooth or gum infection which has led to cellulitis. Nothing to be panic, consult a pediatric dental surgeon and get it evaluated. Mean while you can take a course of antibiotics like amoxicillin(if you are not allergic). If the diagnosis is confirmed as tooth infection, then the tooth has to be treated. I hope i have answered your query. Take care.