A 35-year-old man from rural Maharashtra presents with hypopigmented macules on his face and trunk with loss of sensation. Skin smear microscopy shows acid-fast bacilli (AFB). He is diagnosed with borderline tuberculoid leprosy and started on multidrug therapy (MDT). After 3 weeks of treatment, he develops painful erythematous nodules, fever, and worsening of existing skin lesions. What is the most appropriate next step in management?