Is it safe to leave toilet flange hole unplugged?

[Bienes Raices]

I put some epoxy on the flange to cover a small crack, and it's still drying, so I didn't want to stuff a rag in the hole and mess up the epoxy. I read that sewer gas can potentially cause an explosion (although this house is on septic and it was pumped out a month ago). Are there any concerns leaving the hole unplugged for one night while the epoxy dries? Thanks.