What is this yellow/orange spot on the tip of my tooth? (Photo)

I have had this spot for years now, and its in only one tooth. I think i was told once that it is a type of birth mark on my teeth but it feels rough in that area when i rub my toung against it like if it was chipped but it's not. Its not sensitive or anything it is just stained and feels weird. This is the best picture i could take.