Who is responsible for the medical treatment of a child who got hurt at daycare?

Usually the Daycare would have something about that in their policy, and most often Daycares will have an insurance for that type of thing (injuries to children). Sometimes their insurance will not cover a major accident or injury though. If not, the parents or guardians of the child would be responsible for the medical treatment, but if it was a serious situation you could take it to court and/or sue the company, or put in a formal complaint.