Belly button hernias are quite common in bulldogs. Mom bulldogs are too aggressive when cleaning and if your puppy was free whelped the mom probably was too rough, its difficult for bullies because of the underbite. It would be more of an issue to breed if you had a female with a hernia. Just keep an eye on it sometimes it heals on its own actually most of the time it heals on its own. I had a puppy that had a hernia. I pushed on it gently often so when it closes inside the intestines dont get pinched. If it worries you too much just take him back in to the Vet to be evaluated again. I bet he is fine though. Also I have a puppy that is 6 months old and she never barks. She snores though. My Diva didnt start barking til she was about 1 year. Enjoy the quiet while it lasts.