Hello dear
Lump below yhe neck in child two to three possible reasons ,,,,
thyroglossal cyst ,lymph node and
thyroid swelling
First if swelling move on swollowong its thyroid swelling or other wise thyroglossal cyst,,,
You say below cheek ,,,fever difficulty in swollowing this most probably seems to be lymp node infection or tonsils or
mumps ,,,,in all these conditions symptoms are same go to
ENT specialist ,,,treatment is warm fluids ,antibiotics,anti pyretics,,,,stay blessed