Hi.
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns...
As per your complain a small painless and moveable bump on the face under the skin can be a
LIPOMA which is collection of fatty tissue and is harmless in nature..
In case if it is close to lower jaw line [as you did not describe it is close to which jaw,upper or lower]it can be a clogged duct of
salivary gland which is commonly due t formation of crystalline stones from minerals present in saliva or else can be a
swollen lymph nodes in case if he had any recent infections in head and neck region..
You should consult a Paediatric
Dentist and get her evaluated and treatment can be planned according to the correct diagnosis which can be made only after clinical evaluation..
You need not to worry as mostly such a lump is not a sign of any malignancy and can be treated easily..
Hope this information helps..
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Thanks and regards..
Dr.Honey Nandwani Arora..