If the vet said to give it to him tonight, you really should imo. Just hold his head still and gently slide the syringe in the far back corner of his mouth. The quicker you do it, the better.
He is going to be fine! I have had so many lose teeth like that ... some have lost more. They come to us that way and it is better to get them out...much healthier for them.
Maybe have a drink first!
