Final answer:
The nurse should assess the client's condition and provide appropriate care. Following the FAST mnemonic, the nurse should check for signs of a possible stroke and call for help if necessary.
Step-by-step explanation:
The nurse should intervene in this situation by assessing the client's condition and providing appropriate care. Since the client has facial paralysis and cannot move his left side, it is essential to evaluate his neurological function. The nurse should follow the FAST mnemonic to check for signs of a possible stroke: facial drooping, arm weakness, and speech difficulties. If any of these signs are present, the nurse should call for help immediately. In this case, the nurse should prioritize the client's safety and provide assistance with drinking water.