http://mw1.m-w.com/dictionary/nitty-gritty

Nitty-gritty - "every little, last detail" Once we had been friends for a while, I knew everything about her including the nitty-gritty. Right enough messing about, let's get down to the nitty-gritty with English grammar!

It means the basic or most important details of an issue or a situation: Time ran out before we could get down to the real nitty-gritty.