Kodak did the same thing around 6 mos old and sprained his hip, they thought is was dislocated. I was so upset, so I called the 24 hour emergency number. They told me to wait it out and bring him in the next day.
He was hopping around on 3 legs and couldn't sit. I called another place and they saw him that night, it was sprained and they gave him pain killers. He's been hopping and jumping and leaping ever since!
Here's hoping the little one will be ok, and nothing serious.