Hello there ,
Thanks for writing your query,
Lumps seen in the oral cavity can be of various types .
They can be infective lesions related to tooth like periodontal abscess
or gingival abscess
draining in the oral cavity.
lumps are also formed due to bening or malignant swellings of the jaws .
cysts of the jaws , related to tooth or bone may also lead to swelling .
or it can be a simple bony overgrowth which may undergo remodelling over a period of time as your kid is young.
exact diagnosis can be made only after clinical examination and evaluation by taking radiographs.
i would suggest you to get and OPG radiograph done which will help in diagnosis and accordingly treatment can be planned .
consult an oral surgeon and get the examination done.
i hope this helps ,