This has been growing for a few months now. Started on my left hand nail and has now spread over to my right hand. It only seems to be on my thumbnails though.
Around the same time I developed a nervous habit where I dig my index fingernails into the cuticles of my thumb. I don't know if the two are related, but I'd figure I'd give as much information as I can.
Defiantly looks like some sort of fungal infection like helpful_grey said. I am kind of worried that you are exhibiting clubbing of the fingers though. If there is a history of heart problems in your family you might want to check out a doctor abut both of these problems.