Pine cones are bad for puppies to eat. While they aren't toxic, eating them can cause problems such as intestinal blockages and vomiting. Safer alternatives for chewing exist and care should be taken to avoid pine cones.
The ASPCA classifies pine trees as toxic to dogs and cats, leading to symptoms such as vomiting and depression. This usually relates to pine needles or sap, which may be attached to the pine cone your puppy is trying to eat. Pine cones can also cause intestinal blockages because they are hard and aren’t easily digested. The sharp points may perforate your puppy’s intestines. In addition, anything your puppy eats that isn't formulated for him may make him very sick and lead to vomiting and diarrhea.