A 32-year-old multiparous woman is on postpartum day 5 after a normal vaginal delivery. She is exclusively breastfeeding. She presents with a painful, erythematous, warm, and indurated area in the upper outer quadrant of the left breast. She has a fever of 38.8°C and feels systemically unwell. The infant is breastfeeding well from both breasts. What is the most appropriate next step in management?