Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern.. As per your complain it seems to be a gum boil which can be due to injury to the gums with some hard food or toothbrush bristles leading to stuffing of the bacteria into the gums leading to pus formation.. In this condition localized scaling of the area followed by application of gum pain can help.. Another reason can be a Gingival abscess which is due to poor Oral hygiene and deepening of infection in gums can lead to formation of gingival abscess.. In case case thorough cleaning of the teeth followed by antibiotics and application of antimicrobial dental paste and mouthwash gargles can help.. In case if there is decay in the tooth which is not considerable in your child s case as you have a regular dental checkup profile, buy in case if there is a decay that can progress below root tips of the tooth and cause pus formation and formation of a dental abscess.. If there is dental abscess root canal treatment followed by antibiotics and painkillers will relieve You should consult a Pedodontist and get evaluated and treatment will be done according to the diagnosis.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora.