No problem using the dog chews for horn nocks - part of the fun of having this hobby is finding new ways to repurpose!
You want a great tip though? Go to Hobby Lobby or Michael's craft store and pick up a product called "Amazing Clear Casting Resin" and "Amazing Mold Rubber Kit." (You can also get this stuff from Amazon.com cheaper) Basically, you make a rectangular mold with the silicone rubber the rough size you need for your nocks, and pour the casting resin into it (you can color this stuff too), and you're making your own "bone" or "horn." I know it's cheating, but when this resin dries, it's tougher than bone or horn, it can be glued with epoxy onto your bow, you can color it however you want, and it's just as easy to shape.
For your arrow pass, just carve out a hollow into your bow where you want it, fill it with the colored casting resin, then when it's dried, sand off any overflow, and it looks like a flawless bone inlay.
If you don't mind "cheating" a little bit, this stuff is AWESOME...