It's still exceptionally early for any real diagnosis, because until Nishioka has had his leg examined and it's announced exactly how severe the fracture or break is, we won't know how long he might be out for or how long his recovery might take.
In the skeletal structures you see above, it's the smaller bone that's the fibula. The larger bone is the tibia.
According to most medical sources, a fractured fibula can take between five and seven weeks for a full recovery, although pain may still exist after this time. For more severe fractures and breaks, full recovery to the point of no pain can be up to one year.
We'll update you more tomorrow when we have more information. Until then, good luck to Tsuyoshi Nishioka, and here's hoping this injury is as minor as possible.