Did Fido come limping into the house after running around the back yard? If you've examined the foot and see the toe has a lump or is crooked then he may have a broken toe. If it's after5 p.m. and you don't feel this is an emergency, you can help your dog feel more comfortable. You can put a temporary wrap (you don't actually need to use an actual splint) on the foot that should last until you can call your vet. You will need some supplies from the pharmacy and pet store and a helper to hold your dog while you give first aid.
Put the muzzle on your dog. If the toe is painful any normally sweet dog can and will bite. A muzzle will prevent your dog from biting you or your helper.
Have one person hold the dog. For some dogs, holding treats in front of them will keep their minds off the pain and on the treats, so you can more easily wrap the foot.
Unravel the vet wrap (sold under the name "hurt-free wrap" in pharmacies) and stretch it. This will allow you to tightly wrap the foot without causing your dog to lose blood circulation.
Wrap the foot with the stretched vet wrap by starting in the middle of the foot. Wrap the vet wrap around the foot, then the ankle and a few inches up the leg. Wrap the foot snugly, so the toes can't move. The idea is that you are wrapping the foot, so the surrounding toes work as a splint for the broken toe. The wrap will stick to itself, so there should be no need for tape.
Put the collar on your dog, so they do not chew off the wrap. When you are finished, give your dog that treat he has so patiently been waiting for.