It sounds like too high humidity and maybe some shrink-wrapping if you were opening the incubator. I'd put it in a damp paper towel in a little Tupperware dish and let it finish closing up. You can wet it tomorrow and gently rinse the hardened gunk off.
The membrane dried to the down. And it was in the egg so long it crapped. It happens, usually with waterfowl IMO, not chicks. Looks like it might not have completely closed the naval yet.