Hi Vrae,
I had a large white patch that came up on one of my fingernails, it's in the process of moving down towards the tip, and the rest of the nail seems to be ok. I know fingernails can allegedly tell a lot about your health in terms of their condition, it might be due to a mineral deficiency or something like that.
Is it the nail itself, or the flesh under the nail (nailbed) that is white? If its the nailbed then I think it's probably a blood flow thing (I have patches on my toes where the blood flow is crap and it does look odd), if it's the nail itself then I'd ask your docs opinion.
Sorry I can't really help! Good luck
Bram.