Final answer:
The nurse should assess the infant for pain or discomfort, ensure adherence to pain management protocols, inspect the surgical site, and report findings to the physician, also utilizing non-pharmacological pain relief measures if suitable.
Step-by-step explanation:
The nurse observing a 3-month-old boy exhibiting signs of restlessness, facial grimaces, and drawing his knees to his chest after a pylorotomy should interpret these signs as possible indicators of pain or discomfort. The nurse should assess the infant for further signs of distress, discomfort, or pain by checking vital signs, inspecting the surgical site for normal post-operative appearance, ensuring that pain management protocols are being followed, and looking out for other possible complications. Prompt reporting of these findings to the physician is crucial for appropriate and timely intervention. It may also be helpful for the nurse to provide non-pharmacological pain relief measures, such as swaddling or gently rocking the infant if appropriate.