Hi, his ankle looks normal in the pictures, so hard to tell, and he looks like he walks okay in the video. If the vet didn't notice it, then hopefully it's something minor, or a muscle strain. I would continue to watch it, your the best one to judge if it doesn't look right, as you know your pup, and you see him everyday. If you feel something isn't right, mention it to the vet, and have him check it. Take a video of him on your cellphone of him walking, so the vet can see it. I hope it's nothing serious, and he's okay. Please keep us posted. Sending love, hugs and prayers your way.