My little boy has had a bump behind his right ear from birth. It was tiny at first, and the health visitor said she was definitely not concerned, it was just a fat lump. He is now 6 years old, perfectly healthy, but I notice, and he does too, that it's still there and slightly bigger, more like a small marble now - he says he can move it around, but it starts to hurt when he does - it is on the bone behind the ear. He calls it his 'baby bump'. I keep telling myself it's the fatty lump. But am inwardly worried. Is it fat and will it never get any bigger?