Final answer:
The nurse aide should immediately report a broken side rail to ensure patient safety and prevent potential injuries.
Step-by-step explanation:
When a nurse aide notices a broken side rail on an empty bed, the correct action to take is to report the broken side rail immediately. Ensuring patient safety is paramount, and a damaged side rail can pose a significant fall risk to patients. Waiting for a safety check or attempting a temporary fix such as tying the rail could lead to injury. It's also not sufficient to simply warn the client, as this does not address the underlying safety hazard.