question: MY 3 YR OLD SON HAS HAD A LUMP ON THE HIS NECK ABOUT AN INCH BEHIND HIS EAR JUST UNDER THE BASE OF HIS SKULL SINCE HE WAS 6 MONTHS OLD. IT HAS JUST RECENTLY BECAME A LITTLE LARGER. IT IS KIND OF FIRM AND ONLY MOVES A LITTLE.  IS IT NORMAL? I AM VERY CONCERNED