What do I do if I fell at a gaming casino because of very uneven cement?

This will be a very difficult case.
First and foremost, Indian casinos may not be sued in state or federal court for a slip-and-fall injury: Indian tribes are semi-sovereign entitities (i.e. their own governments, like being their own states or even nations, subject to some limitations) and you would have to sue in the tribe's courts: tribal courts have jurisdiction, or power, over injuries on tribal land, including at their casinos (which are considered tribal land). Not surprisingly, tribal courts tend to favor their casinos, which are major employers and cash cows for the tribes, and getting a fully fair hearing in them when you sue a casino is difficult. In addition, tribal courts operate under their own court rules, so you would need an attorney with experience in this tribe's courts, which may be difficult to find.
Second, while you say the sidewalk is uneven, you'd have to prove that it was "unreasonably dangerous"--more dangerous than is considered reasonable or acceptable in a sidewalk--to win your case, and that may not be easy to do.
Third, you cannot recover for anything associated with your prior fracture--that is not their fault or responsibility. You can only sue for the twisted ankel and wrist and any medical bills (not paid by insurance) you have for them. That may not be enough potential compensation to make suing in tribal court, going up against casino lawyers, worthwhile. You can ask the casino for compensation, but if they refuse or don't offer as much as you'd like, take further action may not be worthwhile.