Yes, PUCK is a Scrabble word!

Letter values in Scrabble US: P 3, U 1, C 3, K 5.

Is it a valid word?

PUCK is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a mischievous sprite of English folklore
a vulcanized rubber disk 3 inches in diameter that is used instead of a ball in ice hockey

Also: robin goodfellow, hockey puck.