I know nothing.
Here's how I arrived at that conclusion.
Consider what matter is made up of. Whenever you look closer at it, it is made up of more nothingness.
And, when you try to look closer at the knowledge you know to figure out what your knowledge consist of, you'll see things you don't know everywhere.
If that's not enough for you, let's consider a math side to this. Let X be the amount of information you know, which is a finite amount. The amount of total information in the universe approaches infinity. So, the amount you know is X / ∞ = 0 = nothing.