Final answer:
The nurse should document the child's self-reported pain level as 4 out of 5 on the chart, but also note the observed behaviors that suggest less pain, highlighting the inconsistency for further pain management assessment.
Step-by-step explanation:
The nurse should document on the child's chart that the child rates pain as 4 out of 5. However, it should also be noted that the child's self-reported pain level appears to be inconsistent with his observed behavior, which includes playing video games and laughing with a friend. This discrepancy should be taken into account when considering further pain management and might require more thorough assessment to understand the child's true pain level and to rule out other factors influencing the behavior.