A hole in my front tooth,cavity?

So my teeth have hardened plaque on them, but i never really brushed or flossed really, so the plaque basically sticked no matter how much i brushed. So a few days ago I saw it started to fade, when I tried to scratch the plaque off my tooth I scratched part off and I saw what appeared as a small hole in my tooth. What should I do, I have already had so many fillings and it costs alot of money?