Final answer:
The most important action for a nurse to take after a breast biopsy is to assess for signs of infection or bleeding, as this is essential for early detection of potential complications.
Step-by-step explanation:
After a breast biopsy, it is most important for the nurse to assess for signs of infection or bleeding. This immediate post-procedure assessment is crucial because it helps ensure the patient's safety and identifies any complications at the earliest stage. While administering pain medication, applying an ice pack to the biopsy site, and encouraging the patient to resume normal activities are also part of post-procedural care, they are secondary to the initial assessment. Monitoring for signs of infection is particularly important, as demonstrated in the clinical focus where a patient experienced redness and warmth at the site of her catheter, indicating a localized infection. Similar vigilance after a biopsy can help detect any adverse reactions swiftly, allowing for prompt intervention.