A 66-year-old patient complains of dense raised induration at the tip of the nose. Protruding part of the induration often breaks off and then continues to grow. Objectively: there is an affected area with focus up to 1 sm in diameter at the tip of the nose. There is a protrusion growing from the focus; the protrusion is 1-1,2 sm high, brownish-grey in colour, with dense consistency. What diagnosis can be assumed?