A 43-year-old man re-attends the Emergency Department a few hours after treatment for anterior epistaxis. The bleeding has stopped. He is systemically well and has no facial pain, swelling, fever or discharge from the skin. He is concerned about a new grey-brown staining around the nostril and upper lip, away from the original bleeding point, after a watery runny nose. The appearance is shown in the image below :

(provided from the rcem safety flash Card ).

What is the most likely diagnosis? Select only one best single option.