Hello,
Your female only laid one egg? Has she attempted to lay anymore eggs?
Is the egg white? Usually they have an indentation but not until they are getting ready to hatch, they will somewhat collapse prior to hatchout. I am not a breeder so I don't have all of the ins & outs of eggs. I will move your thread to the breeding section to make sure some of the other breeders see this.
However if she has only laid one egg I would be concerned about egg binding issues. How old is she? Is this the first time she has laid? I am assuming that she has been mated then?
Tracie