The fan hit his knee on a parked truck when his father pulled him out of the way of the snowmobile, an ESPN spokesman said. The boy was checked out and released to his father.
Australian Jackson Strong was attempting a backflip over his sled in the best trick competition when he got away from the snowmobile. Strong fell to the ground away from the snowmobile, which accelerated toward a fence lined with fans.
Jeremy Bester, of Prior Lake, Minn., was near the fence when the snowmobile crashed through it. He threw his 11-year-old son, Riley, out of the way.
"It really wasn't scary because we're around sleds all the time," said Bester, who added that he stopped the snowmobile.
Strong walked off the course and continued in the competition.