Yes, JOWL is a Scrabble word!

Letter values in Scrabble US: J 8, O 1, W 4, L 1.

Is it a valid word?

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

the jaw in vertebrates that is hinged to open the mouth
a fullness and looseness of the flesh of the lower cheek and jaw (characteristic of aging)

Also: lower jaw, mandibular bone, lower jawbone.

Not playable in Scrabble US: MANDIBULA, SUBMAXILLA.