What Makes Round Holes In Superior Agates?
Agate sometimes contains fossils. Your specimen seems to contain a fossil crinoid disc, and probably there are more than one. Crinoids are plant-like animals anchored to the sea bed, and are sometimes called sea lilies. Many species  became extinct millions of years ago, but a few survive today. The stems of ancient crinoids were made up of stacked discs, rather like the one in your agate. When the crinoids died, their stems often disintegrated, and the discs became scattered. The hole you mention is the hole found at the centre of all crinoid discs. For some reason it did not become full of agate, perhaps because there was a gas bubble or some other obstruction in there. I can't predict what you would find if you cut it in half, that decision is entirely up to you. I think it would probably be best to leave it as it is.