accident on a playground, who is to blame?

In August on a playground my daughter were playing with others children. She's 4 years old. When she rode on a merry-go-round, she was sitting on the chair, it broke and she fell off the chair onto the ground. Unfortunately she hit her head on metal tube and cut her skin head. She picked up by ambulance at the hospital, she  had to underwent an X-ray examination,  detectioned a brise. At the present she's fine, sometimes she's a headpain, we worry about her. From who can we claim a compensation for this accident?