A 32-year-old multiparous woman is on postpartum day 8 following an uncomplicated vaginal delivery. She develops acute onset of severe left-sided breast pain, localized erythema over the upper outer quadrant, and a palpable firm wedge-shaped induration. Her temperature is 39.1°C, and she reports malaise and myalgias. She has been exclusively breastfeeding. Milk expressed from the affected breast appears normal. What is the most appropriate next step in management?