Final answer:
An initial sign of nephrosis in a child is periorbital edema, which the nurse might observe as swelling around the eyes.
Step-by-step explanation:
An initial sign of nephrosis that a nurse might note in a child is periorbital edema. This refers to swelling around the eyes and can be an early clinical indicator of nephrotic syndrome, a kidney disorder which leads to an abnormal protein loss in the urine. It is crucial to differentiate this from conditions that present with other symptoms, such as a rash, fever, or abdominal pain, each of which may be indicative of other diseases or conditions.