My four year old pittbull had major stomach surgery two days ago from eating multiple socks that had him completely full. The surgery went well and his physical condition is good, but his lack of appetite is my concern. How long after a procedure like this will my dog start to eat again. The vet did say he was very lucky to make it through and that he had a lot of brusing and trauma from those foreign bodies...

The general rule is nothing by mouth for 48 hours, however depending on how much damage was done, how extensive the surgery was, and his overall condition at this point in his recovery his vet may see fit to do differently.
Is he still hospitalized and on fluids?
I gather that he is not wanting to eat, is that correct?