Ds is 8. When he was 3 I noticed that on the crown of his head there is a lump. It's hard like a bone. Flew to the drs in a panic and was told it was where his bones have fused together at the top. Said it may disappear as head grows. It hasn't i don't think but he says sometimes that the area is tender to touch. Was satisfied at the time that it is just the shape of his head but now begining to worry that it could be something else? Is this common? Trying not to google.