The patient complains of an inflammatory infiltration in the middle third of the left forearm. It is the first occurrence of this condition in the patient. In the middle third of the left forearm there is an inflammatory infiltration up to 3 cm in diameter that protrudes in a cone-like shape above the surface of the skin. The skin over the infiltration is hyperemic, edematous, its palpation is sharply painful. On the infiltration apex there is a small accumulation of pus with a black dot in the center. Body temperature is 37.6°C. What disease is described?