Hi.. Can understand your concern.. As per your complain a swollen lymph node under the chin can be due to either any dental problem and if it is not ruled out it can be due to infection in other other part of the body. A small painless pimple causing this doesn t seem relevant.. When the lymph draining from other parts of body where there is infection carries infection along and when it is drained in other lymph nodes the infection can settle in those lymph nodes causing infection and swelling.. As per the location a swelling under the chin can also be due to infection in the sublingual salivary gland present below the chin or due to obstruction in the ducts of the salivary gland due to formation of small stones from minerals present in saliva leading to blockage of ducts and back flow of saliva to the gland.. I would suggest you to consult a paediatric dentist or an oral pathologist and get evaluated.. In case if it is a lymph node swelling antibiotics can be given to cure infection in the lymph node as well the part of body from where infection is communicated.. Antibiotics will be needed in case of salivary gland infection too.. In case of duct stones locating the stones and removal can provide relief.. Hope your query is solved.. Thanks and regards.. Dr.Honey Nandwani Arora..