What is this black stuff in my big toenail it doesn't hurt at all its just in the nail?

It is probably just old blood (in other Words, a bruise) from where you banged your toe at some point. It will go away as your toenail grows out. It is not dangerous. Another condition that affects toenails is "fungus" but that usually turns your toenail a whitish or yellowish color.

It is probably NOT blood. I had a black area in my toenail that I ignored. Turned out to be a form of mold in the Pencillium species. Most probably Penicillium chrysogenum.

My problem is after that my nail started to lift up and have stuff UNDER the nail. This may be more of a characteristic of fungus, however penicillin is a close relative but it is easier to treat.

Doctor gave me itraconazole (Sporanox) Three months is all it's going to take.

I can wear sandals this summer!