Pastrnak will be reevaluated in two weeks and is expected to play again this season.
As for how the injury took place, general manager Don Sweeney said it was not suffered during game action. Sweeney said Pastrnak fell while walking to his transportation after a team function and injured his left thumb.
Pastrnak's 31 goals and 66 points both lead the team, while his 35 assists rank second on the squad.
David Krejci had two goals and an assist, Brad Marchand had a goal and three assists, and Danton Heinen and Jake DeBrusk each had a goal and two assists for the Bruins (32-17-8), who have won three in a row and have a point in eight straight (5-0-3).
The Bruins wouldn't appear to be in any real danger of falling out of a playoff spot - they're now fourth in the conference (third in their division) and eight points ahead of ninth-place Carolina - but it could put even more pressure on Sweeney to make a deal before the league's February 25 trade deadline. The Bruins host the Blackhawks on Tuesday night at the TD Garden before hitting the road for a West Coast/Western Conference swing for five games.