A 58-year-old male farmer from rural Maharashtra presents with a 3-month history of a non-healing ulcer on the left lateral border of the tongue. On examination, the ulcer measures 2 cm × 1.5 cm with indurated margins and a granular base. There is ipsilateral submandibular lymphadenopathy. Intraoral examination reveals no other lesions. What is the most appropriate next step in management?