My right index finger nail has been getting chewed by something and now I think my pants zipper is the culprit. Is this a universal problem that everyone knows about except me? I haven't caught my zipper in the act yet but I can't think of any other cause. It only seems to wear the fingernail one the middle finger side of the nail. It is a gradual wear, never suddenly conspicuous, so it is hard to tell what is causing it.