Is this dandruff?

I have recently been scraching my scalp and I have long nails so this white sand like stuff is under there adn when I did it out from under my nailsa and put it on my hand it looks like a massive amount is it dandruff or somethign else and di this come out of nowhere kuz this usually hasnt happened before
HELP

From what you've said It's more likely dandruff--there are a few other dermatological issues that could possibly attribute to this such as psoriasis (not likely it is, however). Depending on where your geographical region the winter months can be very bad on your skin and there are a number of OTC products that can help restore moisture to your scalp or skin--just ask your doctor or local pharmacy/pharmacist. Those products should resolve your problem or reduce them to a manageable level. Always see your doctor if you feel the issue could be more serious or if you can't resolve it or have more questions. Take care. :-)