A hole in my yard.

As I see when you people moved in to this house the hole was already there in the yard, so if you are quiet sure that it’s not done by the dog then fine or else it would come as your fault. Now you can talk with your home owner and asked him to fill up the hole as it was only done with gravel and which gets removed quickly if not fixed out properly.
I am not a lawyer or legal person.. so nothing strong or review you can take from here, But I can provide you my good advice. Also as it is 3 years long time.. so I think some of the maintenance should have been required, so you can talk with the landlord and if they are not filling up the hole for your yard, you can report the landlord or file a complaint. Here mostly only a mutual understanding is required between you and owner, and it will get resolved. However if landlord is not responding correctly or not showing any sign that he will fill up the hole.. I can say you can try this site’s report filing page.. It is good and has options to file a complaint and they take care of rest of the issue.. Hope your problem would also gets solved by them.. Because filing a complaint with police or any lawyer will take up a huge amount and time, also this seems a less problem… however to an extent not because your mother fallen down on stepping to this hole. so this is bad for your family.

https://www.rentalprotectionagency.com/complaint_center_form.php Please check this link could be helpful for you