Yes, EGOISM is a Scrabble word!

Letter values in Scrabble US: E 1, G 2, O 1, I 1, S 1, M 3.

Is it a valid word?

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

(ethics) the theory that the pursuit of your own welfare in the basis of morality
concern for your own interests and welfare

Also: self-interest, self-concern, self-centeredness.