A 30-year-old patient complains about body temperature rise up to 39,0°C, a roundish infiltrate on his upper lip, general weakness. He has been presenting with these symptoms for 3 days. Objectively: a roundish infiltrate in the region of the upper lip 2,5 cm in diameter, the skin over the infiltrate is red with a necrotic core in the centre. The upper lip is hyperemic and edematic. What is the most likely diagnosis?