I have discovered a patchy brown spot on the side of my index finger. It has different shades of brown and is worrying me as I can not stop thinking about it since I first discovered it. It is about 3-4 or even 5mm wide. What are all the possiblitys and the most likely thing this could be? I am an 18 year old male and have become very stressed over this

Also if this is some form of cancer how can it be cured if it can? I hate using the 'C' word