I have a black spot under my bigtoe, its not a round spot it is like a tiny little asymmetrical line, its only about 1 and a half millimeters and it doesn't go up and the surrounding area under the nail is a tan color and it kind of looks as if it is hollow, like its eating away at my nail from underneath, I have not hit it recently and it is not painful or swollen, the black spot has a defined boarder with light brown or tan discoloration surrounding it no other symptoms.