Sometimes an egg gets an incomplete calcium coating while passing through the shell gland, the end of a long 24 hour process to create an egg. I have a five-year old EE who has problems in her shell gland and she sometimes produces eggs with a pin hole in the end like the one you've shown us. Most of the rest of the time, her eggs have calcium deposits at the end, resembling bumps and pimples.
If it happens a lot, it's an indication your hen may not be properly absorbing calcium.