A 28-year-old man from Delhi presents with severe left-sided throat pain, dysphagia, and fever (39.2°C) for 4 days. On examination, the left tonsil is enlarged, erythematous, and displaced medially. The soft palate is pushed downward and medially. Intraoral palpation reveals a bulge in the left lateral pharyngeal wall. What is the most appropriate next step in management?