<s>[INST] Hi, My son is 18 months old and cutting 4 molars at one time 3 have surfaced but one had a bubble that formed on his gum, the Dr. called it an eruption cyst he has had a fever of 101.0 F. and is very very fussy, he will not take any pain medicine, he does not want to eat, but he will still nurse. We checked the spot and now it is filled with whitish yellow puss, do we need to be concerned now? [/INST] Hi. Welcome to Chat Doctor . I have gone through your query and can understand your concern. As per your complaint it seems that a bubble on the surface of the gum with signs of teething seems to be most probably an Eruption Hematoma or an Eruption cyst that occurs as a fluid filled pale colored lump, and it is not a harmful condition and will resolve as the tooth will erupt. The first tooth to erupt in mouth is at the age of 5-6 months and is lower front tooth. But in case if there is any problem associated with it or the tooth gets delay in erupting then it has to be removed to let the tooth erupt in the mouth and once the tooth erupts there is no further problem associated with it. Fever can however be due to teething but can also be due to viral infection and for this you can give him Acetaminophen but if the fever does not resolve or exaggerate then consult a Pediatrician. Hope this information helps. Thanks and regards. Chat Doctor.  </s>