Nielsen beat Boston goaltender Anton Khudobin glove-side.
It was his 14th goal of the season and 150th of his career.
Unfortunately, Nielsen was not able to build on that as David Backes hit him in the Detroit end along the boards with 11.2 second left in the first period.
"It's an unnecessary hit to the head," Wings captain Henrik Zetterberg said after the game. "He's a big piece of us. Now he plays in all situations, PK, power play and shut-down guy. We'll see how it is. Probably got to see the doctors on where to go from here but obviously that was a big loss for us."
Detroit athletic trainer Piet Van Zant rushed to Nielsen's side and helped him off the ice.
Early in the second period, the Wings announced Nielsen had an upper-body injury and would not return to the game.
"It's terrible," Anthony Mantha said. "I didn't really see the hit but I think it was a cheap shot to the head. Obviously Niels is a big player for our team. He's been playing great lately. Power play time also, first goal tonight. It's hard to lose him for sure."
After the game Wings coach Jeff Blashill said he did not yet have an update on Nielsen's condition.
"I don't have an answer on that," Blashill said. "I only knew that he wasn't available the rest of the game. I assume that probably means that he might be out for a little bit, but I don't know that answer."
Martin Frk took Nielsen's spot on the power play.
Nielsen finished with eight shifts for 5:22, scored the goal and won 4-of-6 face-offs.
The Wings have Wednesday off and host Tomas Tatar and the Vegas Golden Knights on Thursday.
