Very carefully you need to check the eggs that have not hatched. Very carefully.
There will be a small after a hatch but nothing like you describe. What I suspect has happened is that one of the eggs has bacteria in it. It is now officially a rotten egg. As such it is dangerous. Please be careful. I’m really not trying to be funny.
When bacteria get inside an egg in an incubator it multiplies like crazy. The egg material is a perfect nutrient medium for bacteria to grow. The incubator temperature is the perfect temperature. Scientists often use eggs at incubator temperature to culture bacteria. When that bacteria grows, it produces gasses. They can build up inside the egg to the point it explodes. Sometimes liquid will ooze out of the egg, foul smelling liquid.
What you need to do is very carefully get that egg out of your house. Now! It could explode at any time. Do you want that thing to explode in your house and distribute that smell everywhere? I didn’t think so.
I’d probably rap that incubator with a towel or something to try to contain it if it does explode and carry the whole thing outside. Once outside you can identify which egg it is by sniffing them. Get rid of it. Burying it deep is probably the best option. If I were hauling your trash, I would not want that smell in the trash.
You can do with the other eggs as you will. In my experience they are not likely to hatch unless you put them in at different times. Or you can do the float test. That’s where you put an egg that has not pipped in a calm bowl of water. If the egg wriggles, something is alive in there. If it does not wriggle after a few seconds, nothing is alive in there. You can put any that wriggle back in the incubator if you wish, but I’d probably just ditch all the eggs and figure out how to clean and air out that incubator to get rid of that smell.