Put a bunch of Quik Stop on gauze have someone hold him while you do this. Take gauze and wrap up his foot and up his leg about 3-4 inches. Then wrap with tape. The Quik stop will stop the bleeding. Remember to not wrap too tightly. This will get him through the night. Call your vet first thing in the morning. My Sammy just did a similar problem with a nail 3 weeks ago. Hugs to you and your little one...
