It's the big toe of her left foot.
http://gulfnews.com/sport/athletics/dibaba-will-be-back-in-action-soon-says-coach-1.1810302?
“Luckily, it is nothing serious and we heeded to the doctor’s advice of staying back in Addis Ababa,†Aden told Gulf News.
“At the most, she will be out for the next two weeks, and this is a big risk for us especially because it is a few months before the Olympic Games. But the good thing is that she is able to keep working on her endurance training by cycling and going to the gym,†he added.