Two workers were on the right-hand platform of a continuous miner.

Without warning, a greasy back - an insecure piece of roof material - gave way.

The miner driver jumped back but was hit by falling material.

The worker was left winded and sore and suffered bruising and scrapes.

The NSW Resources Regulator said the worker was cleared of serious injury after being assessed at hospital.

"Workers must always be alert to the hazard of unsupported ground and must remain vigilant of their position relative to the risk of unsupported ground failure, which may occur without warning," it said.

"Operators should review the appropriateness of the equipment they have provided to workers to install the required ground support in a timely manner at all stages of the production cycle.

"If the appropriate equipment for the prevailing conditions is unavailable, work should not continue."