Yes, BEGAN is a Scrabble word!

Letter values in Scrabble US: B 3, E 1, G 2, A 1, N 1.

Is it a valid word?

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

take the first step or steps in carrying out an action
have a beginning, in a temporal, spatial, or evaluative sense
set in motion, cause to start
begin to speak or say
be the first item or point, constitute the beginning or start, come first in a series
have a beginning, of a temporal event
have a beginning characterized in some specified way
begin an event that is implied and limited by the nature or inherent function of the direct object
achieve or accomplish in the least degree, usually used in the negative
begin to speak, understand, read, and write a language

Also: get down, start out, set about, set out, lead off.