Hayward played 31 minutes in Boston's 117-106 win, finishing with six points, five rebounds, four assists, and three steals.
Celtics head coach Brad Stevens told reporters earlier that he expected Hayward to return, but the forward would have the final say on his status.
"I anticipate he'll be available, but that's his call," Stevens said, according to ESPN's Malika Andrews.
Hayward would also have his minutes monitored in Game 3, Stevens added.
The team was reportedly optimistic earlier that Hayward would be activated barring a setback in the pregame warmup, sources told ESPN's Adrian Wojnarowski.
Hayward hadn't played since Boston's first playoff game against the Philadelphia 76ers on Aug. 17, when he suffered a right ankle sprain. The injury forced him to leave the NBA's bubble for treatment.
Marcus Smart has been starting since Hayward's injury.