I have never had any experience with this either, but I do know one thing. A long time ago, back before I began teaching young children, I was a live-out, full time "Nanny". I was this children's Nanny for 3 1/2 years and one of the boys broke his arm jumping off a swing ( that I told him not too, because he was wearing flipflops and the grass was wet !) and at first when he came in to show me, I really did NOT think it was broken. It turned out that he had broken it right in half close to the elbow !!
My point is that you can never really tell if a limb is really broken. I am pretty good at first aid and things of that nature and I was fooled.
Anything is possible. He could just have one leg a bit shorter than the other. If it is a sprain, if he is "favoring" it somewhat it might be a sprain, and he might be in pain. They don't exhibit symptoms like other animals do, they hide them- due to their prey animal instincts, like with illnesses too.
I would give it a day or two more..and if he still seems to be limping I would take him in to your Vet. Have her take a x-ray though so you are certain nothing is broken. A slight fracture would be even harder to tell without an x-ray. So my friend, those are my thoughts. Hope I helped a little bit, anyway...
