Suggest Treatment For Greyish Discoloration Of The Toenail

My toe nearest to the pinkie toe on my left foot is discoloured on one side. It is a greyish colour and there it's been there awhile. I am only in my late teens so I don't know if it's a health problem, or if it is just a dicolouring from a blow the the nail. Also, the colour is not from under the nail... the colour is acutally IN the nail. When I clipped my nails, the colour was visible.