Jason Terry was on the receiving end of J.R. Smith’s boneheaded Game 3 elbow. That was just one reason Terry and the rest of the Celtics, facing elimination, were ticked at the Knicks. Terry stressed being angry was one thing, doing something about it was another.

Yesterday, Terry did something about it.

“You’re down 3-0,” Terry said. “That angered me. Looking at that reality that it’s over. Like, the season’s over. Everything you’ve worked hard for is done,” said Terry, who claimed Smith’s elbow “maybe made us have a sense of urgency, which we’ve been lacking.”

Terry and the Celtics knew the danger going in: One more loss to the Knicks in the first round playoff series meant the summer would begin in April. After a disappointing regular season, Terry realized redemption could be found on a big stage. And here the stage was biggest.

“He was huge, bigger than anybody,” teammate Kevin Garnett said of Terry.

Terry scored nine of his 18 points in overtime, including a transition 3-pointer and a 2-point jumper 42 seconds apart, and the Celtics averted a sweep by holding back the Knicks, 97-90.

“I had every intention of trying to make an impact on the game some way or another. If I wasn’t making shots, I wanted to get a steal. I wanted to get a rebound. Just any little thing to prolong this season,” Terry said.

He kept it going. Maybe Smith’s elbow was motivation.

“It hurt. I mean, it hurt. It still hurts right now. As long as I feel that, I guess I’ll be thinking about it,” Terry said.

And talking about it.