Thanks for your query.
He most likely suffers from "herpetic gingivo stomatitis" a common infection at this age caused by herpes simplex
virus . There is inflammation of the gums and lips caused by the herpes virus. The same virus causes cold sores. These ulcers are painful and often lead to drooling
and refusal to eat or drink. The blisters usually take between10 -14 days to go away. The blisters never leave scars.
Regarding management you should use panadol
every 4-6 hrs for pain & do all you can to encourage your child to drink. Antibiotics and antiviral
medications do not work and have no role in this condition.
hope you find the information useful.