I also think there is no health issue there whatsoever. It looks like that area is simply void of the yellowish pigment(xanthine/erythrins) and you are actually seeing through the parietal scales on the head into the soft internal head tissue, etc....It is very typical on young snakes to be able to see through their much thinner scales into the blood and tissue giving them a pinkish/purple hue. Just like in many extreme hypos and amels you can see their eyes through the top of their skull, especially when very small.
There are also certain conditions in the pigment cells (chromatophores) of snakes that can cause them to actually lose coloration instead of gaining more. Not much is really known about this, but lacking pigment of any type alone is not cause for any worry.
Take some pics and save them to refer to later as it matures so you can compare notes on the progress. I have seen certain snakes start out completely normal, or just slightly void of pigment here and there, and later as they mature be completely "calico" and look like a totally different animal altogether. Nature is truly bizarre, and no human will ever completely understand alot of it.
~Doug