Sometimes, the egg-laying mechanics of the chicken go wrong. It's possible that the tiny egg will have no yolk. It is probably just a once-in-a-blue-moon thing, and nothing at all to worry about. Blow the egg out, save it, and have a trophy of a tiny egg. ;O)
I have gotten a couple of these out of my hens. they have had yolks in them and they were very delicious. They were very "rich" in flavor. Yummy. Make sure that when you crack it open, make sure that you do it into a bowl by itself to be on the safe side. By all means if you can cook it, do it and enjoy it.