After his battle with Zoom, Barry (Grant Gustin) was left without feeling in his legs. In case you were worried, don't be; he's got a very fast metabolism, and he heals pretty fast. His broken back is already mostly stitched back together as this episode opens.
However, while Barry is almost walking, his running speed isn't back. It's not the physical damage, but the emotional damage that leaves The Flash crippled. He was dragged all over Central City by Zoom, and the city that depended on The Flash to be their hero has now seen him defeated, and that has given him a mental block about using his abilities.
(By the way, this isn't the first time the hero has faced this kind of a physical challenge.)