What is the skin growing under my toe nail? It is hard looks kind of a bubble its been like this for several months and the toe nail is rotten nd the skin under it has grown

Fungus. Is most likely cause. See podiatrist or dermatologist.
If . If the growth is hard, the most common type of growth next to or under a nail is a periungual fibroma, a benign growth that usually is painless, but unsightly. They are easy to remove, especially if the nail itself doesn't need to be removed as well in order to get the entire lesion. I assume there is no pigmentation, discoloration or oozing coming from the area, as any of these symptoms can be a sign of something more serious. A dermatologist or podiatrist can tell you for certain what it is, and can also either remove it and/or biopsy it. It's not a big deal, and recovery is fast and easy.