A 50-year-old man who works as a cook complained a greenish discolouration of his right thumbnail. He could not call any history of trauma. There was no pain and discomfort. Physical examination reviewed a greenish patch under the right thumbnail plate with mild onycholysis.

What could be the most probable diagnosis for this condition? *This image based case is from Docplexus editorial team for educative purpose only. Source: Haymarket