<s>[INST] we found a hard lump under my sons jaw and it has tripled in size over the last week. We are taking him to the Dr this week but in the mean time we are very anxious and worried about it. It's slighlty tender to the touch but he is otherwise a very active and healthy 8 year old. [/INST] Hi.If it is not increasing with chewing / eating , it is most probably an enlarged lymph node.Mostly caused by the caries tooth or an injury to the oral mucosa.Antibiotic course along with the anti-inflammatory medicines should solve this. Take him to the Doctor earlier. </s>