Final answer:
The nurse should record an evaluative statement in the patient's care plan following the successful self-administration of insulin by the patient.
Step-by-step explanation:
Following the observation of the client successfully administering insulin, the nurse should record an evaluative statement in the client's plan of care. This documentation is a critical part of the nursing process, ensuring that progress is accurately tracked and communicated across the healthcare team. It is important to keep the outcome in the client's care plan, as ongoing assessment and reinforcement of the skill may be required to ensure the client retains the ability to self-inject insulin effectively. Further reassessment could be necessary to ensure that the client maintains this competency over time, especially under different circumstances or if any changes in the client's health status occur.