Thank you for your question, I'm Dr. Dan and I'll try to help you.
At this point a single streak of blood is not a big deal or an emergency. What is likely happenening is that he's exeriencing a mild colitis due to the bone or something else he ate. In dogs bright red blood in the stool is not nearly as threatening as it would be in humans. There is a good chance this won't occur again! If you see the stool start softening more and more, or his appetite drops, or you see a couple more stools have blood in it, then it is time to see the vet. In most cases short term antibiotics is all that is required to get this back under control. I'd keep an eye on him for now and watch for the symptoms I mentioned, but that's all you need to do right now. I hope this helps, if not please feel free to ask more questions, if it did, please leave a rating. Dr. Dan
You are quite welcome!