I would have him check it out! My son had sagittal synostosis and had to have surgery at 6 months. My pediatrician noticed it at 4 days and watched it at 2 months and then referred me to a neurosurgeon who then watched it until at 5 months it was closed enough that it was starting to cause pressure on his brain. This is NOT something to play around with. It is a lot easier to get a second opinion or have them check it out. I have had other people email me (since posting on my blog about it) and tell me that their doctor didn't notice till after a year or so and that their options were limited. The best time (if they have to have surgery) is between 6 months and like a year because their bodies can heal.
Anyway, I hope that it is nothing, but if it isn't, NOW is the time to get it checked out and to keep it monitored. My mom also noticed from the very beginning and was happy that the doctor said something!
One more thing...I had Kaiser and have good references to doctors if, by chance, your daugther/son has Kaiser too.
Good luck! :) A.