A 28-year-old woman from Delhi presents to the emergency department with a 2-day history of severe pharyngitis, fever (39.5°C), and difficulty swallowing. On examination, she has exudative pharyngitis, enlarged tonsils with purulent exudate, and tender anterior cervical lymphadenopathy. A rapid antigen detection test (RADT) for Streptococcus pyogenes is positive. She has no history of penicillin allergy. What is the most appropriate immediate next step in management?