Thornton, the team's captain and leading scorer, took the opening faceoff against the Montreal Canadiens.
Thornton was hurt Thursday night against the Washington Capitals when he fell after being hit on the wrist. He missed games Saturday and Sunday. Neither he nor coach Mike Sullivan gave details of the injury, but it was thought to affect his ribs or wrist.
Thornton practiced with the Bruins on Tuesday for the first time since he was hurt and said he would wait until Wednesday morning to see how he felt.
"The pain I don't think will be a problem," he said after Tuesday's practice. "Just to see if I can actually go out there and move the way I want to move and things like that" was a greater uncertainty.
Thornton led the Bruins with 23 goals and 50 assists this season and missed just five games.