Yes, STUBBLE is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, U 1, B 3, B 3, L 1, E 1.

Is it a valid word?

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

material consisting of seed coverings and small pieces of stem or leaves that have been separated from the seeds
short stiff hairs growing on a man's face when he has not shaved for a few days