Big toe nail very painfull to touch

If you are asking for a list of possibilities which might result in pain of a toenail, clearly there would both be far to many possibilities, and that would not be helpful to you. If you are attempting to have a responder suggest to you why YOU might have this problem, that would be an unreasonable expectation.

What to do? . . . See a doctor who might be able to answer your question based on an examination and history.