Agree with the others who say that all you can safely conclude is that he's pointing because he is sore. Beyond that you just need to get a vet to diagnose. I've seen horses point with navicular, early laminitis, hoof abscess, and sinking pasterns/suspensory issues. Like an earlier poster, given the morgan/perch breeding, laminitis would be one of my concerns and I'd put her in a drylot with soaked grass hay immediately just to be safe.
The below list is probably stating the obvious just as much as the above statements, but here are some things I ask/test when a horse is off. I think my vet appreciates this information when I'm making the initial call for a farm visit:
heat/swelling in the soft tissues? heat in the hoof? strong digital pulse? How does lameness "behave" relative to work--does he improve after warming up? Any change in symptom on hard vs soft surfaces? Walk or trot him on a longe-- is it worse in a certain direction? Does head bob up or does he lower his head down when stepping on affected leg?