An entrance door to the Cyclone ride dislodged and struck the wall of a stall inside the ride, Kris Reyes, Boardwalk spokesperson said.
"It somehow impacted one of the stalls that the riders stand in. The wall of the stall is what caused the injury to the child," Reyes said. "The wall sort of buckled."
A centrifugal-force based ride, Cyclone riders stand in stalls with their backs pressed against the circular structure. They are held in place by the centrifugal pull as the ride spins, rises off the ground and tilts sideways.
The boy who was hurt is believed to be about 9 years old, but Boardwalk officials are not certain, Reyes said.
"He was treated for minor injuries at the scene by paramedics and released to his parents," he said.
The ride was shut down immediately and evacuated. It remains closed for the foreseeable future.
Once officials from the Boardwalk and the state Division of Occupational Safety and Health determine what went wrong, they will decide the future of the ride.
Two nearby rides, the Convoy and the Tornado, were temporarily shut down shortly after the Cyclone was halted. Both have since been reopened.
No other rides have been affected.
