Sorry it didn't make it, looked more like a slug then a boob egg. But Boob eggs can be treated with liquid bandage, apply it to the affected area only before you see any signs of molding.... in other words, apply it as a preventative treatment.

The other point I'd like to make is, try to keep the nipple above the substrate. So that it doesn't get any form of moisture coming into contact with it.

When you get to the last few weeks before hatching, you may notice a small patch of mold develop... scrape it off. You may have to do it each day.... but do it. May not happen either.

But it works, may not work every time.... but it's better then sitting back and watching that boob egg go bad without trying.