Skip it and for future reference as well: if you accidentally miss a dose, relax, and just pick up again at next schedule time after eating. While it is always best to never miss a dose, that would be unreasonable to think we all don't miss it from time to time (I've had a few myself, having a diabetic cat in my household). It happens to us all. But you don't want to give it at an odd time, throwing off the schedule and possibly causing hypoglycemic reactions too. Just don't worry, that dose was skipped, and pick up again in the morning after his breakfast. Better to let the sugar be high for the night than too low and more dangerous.
Best of luck. Let me know if I can help further with anything,