Final answer:
The nurse should document the non-blanching redness over the trochanter as a Stage I pressure ulcer, indicating the beginning stage of a bedsore.
Step-by-step explanation:
After observing that the area over the trochanter is red and does not blanch with finger pressure, the nurse should document this as a Stage I pressure ulcer. This is because bedsores, also known as decubitus ulcers, begin as areas of redness and non-blanching erythema on the skin, especially over bony prominences, and can progress to more serious stages if unrelieved pressure continues. Early recognition and documentation are critical for initiating appropriate interventions to prevent further tissue damage.