A 28-year-old man complains of painless sore in his mouth that persists despite the attempts at self-treatment. Objectively the regional lymph nodes on the left are enlarged and painless. Mucosa of the left cheek presents with round ulcer, 1 cm in diameter, with raised margins and cartilage-like infiltration in its basis. The surface of the ulcer is colored meat red and painless on palpation. What is the most likely diagnosis?