Serial Casting setback

This last casting Jonathon started to complain of pain in his left foot. So so much so that he refused to walk anymore. For almost two days Jonathon would crawl around the house on the floor not putting any weight on his left foot at all. I just knew something was really wrong I almost cut the cast off myself. I continued to check his circulation and it was fine. So Monday afternoon I took him into his PT to have the cast removed. I gave him a piggyback ride to and from the car. When his therapist used the cast saw and cut the cast off we half expected to see a wound of some sort but it looked fine. Then we felt it and his foot was hot. It was also swollen. His PT had to get a colleague and they decided that he must have strained it somehow and we need to let it heal up before we cast it again.
What does all this mean? It means that we've taken a step backwards. If the casting dosen't work then we'll have to do surgery. I'm so confused. I don't want to put my son through a major ordeal of having a surgical procedure on both of his legs. But then I ask myself what am I doing right now? I pray everyday that I'll know what to do.