See the candling thread, or google blood rings in eggs. I'm new too, but from my understanding a blood ring is where the blood has drained away from the dead embryo. It will develop bacteria and not taken out of the incubator will likely explode, ruining your hatch. All eggs will have to go.
An embryo should be filling most of the egg by day 14 (see candling thread here again, it's s sticky on top of the forum page) and should be from the pointy end to the air cell at the bottom.
I don't know for sure, but if you have an air cell at the pointy end too I'd say your chick has died a few days ago. The blood ring is the evidence, and as bacteria excrete gasses this can lead to a gas build up inside the egg.
It sounds to me like you've lost this one, but wait for someone more experienced than me to tell you that unless you chuck out a viable egg.
Does it smell? Is the floating embryo moving on it's own - if you candle it and hold the egg still for a minute does the embryo move? Even a little shiver means it's alive, mine are day 15 and when I checked them last night, they were filling the egg pretty much and just shuffling around a little.
