Opinions On What This Could Be

[Prostheta]

cant feel it at all, it seems very slow moving if its fungus and the neck has always been cleaned well, im tempted to try and bleach it to see if it will dissapear.

another option is to just get a new neck, i was never fond of the shape anyway its quite a fat C shape and i like V shaped necks with a nice round radius on the fretboard, the one i have now seems flat as a witches tit.

I thought witch tits were cold, not flat. So they're cold AND flat now? Bummer.

[Dean]

It could be that some mosture was on the neck before sealing...and it is starting to grow fungis.I would sand a spot and see if you can sand it out,and reseal.