A 28-year-old woman presents to the ENT clinic with a 4-day history of severe sore throat, dysphagia, and fever (38.5°C). On examination, she has bilateral tonsillar enlargement with yellowish exudate, cervical lymphadenopathy, and mild trismus. Throat culture grows Group A Streptococcus. She is started on oral penicillin V. On day 6 of illness, she develops severe unilateral throat pain, difficulty swallowing saliva, and a muffled voice. Intraoral examination reveals bulging of the soft palate on the left side with displacement of the tonsil medially. What is the most likely diagnosis?