This can mean it's hatching but if you picked it up and see no slit or egg contents leaking out then I'd suggest misting the container a bit to add some moisture back in(not misting the egg itself TOO much), the dimple should pop back out. When you're expecting eggs to hatch you tend to be opening and checking more often so the humidity drops. I always wipe the condensation from the top of the lid when i open to check, that way the water won't drip down onto the eggs causing mold.. but then I add water back into the substrate to replace what I removed.
Good luck & let me know how it goes!