It isn't really uncommon for a puppy to investigate his poo. They do make supplements (S.E.P by Solid Gold as well as others) that stops the poo eating but there are a couple of other remedies to help stop it.
First of all, keep it cleaned up as much as possible. Some people add a bit of meat tenderizer to the dog's food as it make the poo taste horrible (from what I hear anyhow

) but I think there is too much salt in it. Pineapple is what we used. My Abbie was a poo eater and after adding a few chunks of canned pineapple to her meals, she quit.
It really isn't that big of a deal, you just want to have your pup stop doing it before it becomes a habit.
BTW, it is called coprophagia...that may help you in internet searches.