Hi there, my name is ***** ***** I am a registered veterinarian and I would like to try to help you/
We can see this type of behavior post surgery when patients are stressed or painful. I think it is worth discussing your current pain medications with your vet in the morning to see if they may need adjusting.
You could also try getting some Zylkene caspsules. They are made with milk protiens that can help to reassure your pet and help him feel safe and secure. He may feel a little stressed post operatively as it is a change in his normal routine. It is natural, non-sedative and available over the counter.
I hope this is helpful information. I hope your little one feels better soon. If you need anything else at all please don't hesitate to reply. Please don't forget to rate/accept my answer if it has been of use.
All the best with Cato, Sophie