question: hi, my 3 yr old has a small grape sized hard lump on the outer surface of his upper rt arm. he had a insect bite in tht area 7 months ago but it didnt seem to resolve and has now grow to 2.5 cm in diameter n looks pustular but is hard on touch. should i be worried. it keeps getting bruised when my son bumps into things while playing. what else cud it be? dd?