Puppy’s Behavior Has Changed After Neutering

Our puppy is 7 months old, and he was neutered at the same time he had stomach surgery, so I know it was a lot for him. But his behavior has changed so much since then. He’s started nipping again, even though he had stopped that before. He’s not listening as well, and he’s barking at us when we tell him “no” or when he’s biting. I’ll remove my hands, and he’ll start barking at me, whereas before, he would just stop and calm down. He’s also started chewing things he never touched before.

It’s only been 3 weeks, so maybe that’s why, but I’m lost on what to do.