A 60-year-old patient addressed a dentist with complaints of a conic protrusion appearing on the skin of his chin on the left. Height of the protrusion is 1,5 cm, width - 0,8 cm. Palpation is painless; there are clear margins; the protrusion is gray-brown in color; on palpation of the soft tissues near the protrusion base a thickening can be detected. What preliminary diagnosis can be made?