The blood in the stool can be a sign of food poisoning. I had no idea that is how food poisoning shows up in dogs/cats until mine got it. Eating grass is a good thing for them to do as it settles their bellies. Just make sure the grass hasn't been treated by chemicals.
You may give the dog some Pepto Bismal if you think the dog just ate something that didn't agree. Maybe ate some bad table scraps.
However, the dog may be allergic to milk, eggs, yeast, or other ingrediants in it's food. That will require a vet's visit and a watchful eye on it's diet. Be careful the dog didn't eat chocolate or a strange plant. This will take immediate trip to the vet.
To induce vomiting give the dog a teaspoonful of Hydrogen peroxide. May give more to a bigger dog but NOT too much. The dog will vomit within about 10 minutes. My Scooby ate chocolate chip cookies while I was talking to a neighbor. He didn't like "tossing his cookies" but I felt better.
Good luck!