Legal Question in Personal Injury in California

Tender it to your homeowners' insurance carrier. They will sort it out.

Potentially. You, as the owner/occupier of real property, owe visitors a duty to protect them from hazards associated with the property. So there's a potential liability. It's the same as if someone gets injured on a trampoline in your back yard.

On the other hand, there's also a potential defense, "assumption of the risk", in which a person undertaking an activity is assumes the risk of injuries that that typically result from such an activity.

So what it really comes down to is this - if they want significantly more money than your home insurance deductible, contact your insurance company. If they want less, then consider either paying them off or making them decide whether or not to sue you in Small Claims Court.