Dog Aggression?

I picked Duncan up from the vet this morning after being neutered and we came home and took a nap. ( I worked nights) Well when I gave him a bone to keep him entertained, he was acting aggressive towards stella and she was keeping her distance. when I went to take it away he attacked me and tried to bite me. I'm wondering if he is out of sorts from the anesthesia or the fact that he lost his manhood? He doesn't act in pain at all, he is quite hyper. Anyway, he kept doing the attacking to my husband and myself. i hope this isn't a problem brewing. I can't handle another dog with psych issues, stella is a scardy dog (part shar pei). Any one have any experience in this?