According to the official statement:
"Harrison Ford sustained an ankle injury during filming today on the set of Star Wars: Episode VII. He was taken to a local hospital and is receiving care. Shooting will continue as planned while he recuperates"
This isn't the first injury for the actor - he famously required major surgery during the Raiders shoot - but it does prove to be a bit disconcerting for the well being of this rogue pirate/smuggler-turned-General of the Rebellion-turned-whatever he's going to be in this film.
We wish Mr. Ford a speedy recovery, and hope he gets back on his feet again soon.