The guy who got a million bucks for selling the record-breaking Powerball ticket didn't spend the dough on a new car or a fancy vacation ... so says his son-in-law, ex-NFL star Domata Peko, who tells TMZ Sports he gave $100k to his grandkids instead!!
Joe Chahayed -- who owns the Joe's Service Center gas station in Altadena, CA -- was the man of the hour in November ... after it was announced his shop sold the $2 BILLION ticket.
We spoke with 38-year-old Peko about Joe's million-dollar payday .