Yes, CUPID is a Scrabble word!

Letter values in Scrabble US: C 3, U 1, P 3, I 1, D 2.

Is it a valid word?

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

(Roman mythology) god of love; counterpart of Greek Eros
a symbol for love in the form of a cherubic naked boy with wings and a bow and arrow

Not playable in Scrabble US: AMOR.