My 4 year old has a puss filled ulcer on his gums that wont go away. hes had it for almost a year, he had antibiotics a few weeks ago that alnost clearred it up. but nt fully. now its back, what can we do

Treat tooth: The antibiotics are only a bandaid and will not make the infection go away. Your 4 year old needs to see a pedodontist and get the tooth treated. Also he needs to start regular dental care or these issues will affect his permanent teeth.

See dentist: Sounds like you need definitive treatment and not symptomatic treatment. You need to see a dentist and have thorough exam, diagnosis, and treatment, before that small little (likely) infection turns into a huge life threatening abcess, or it may not even be an "infection", a dentist needs to see you.