Rabbits won't usually want to eat peed on hay unless they're starving. So try and keep the eating hay pile to a less peed on corner. Then there is always the excess hay that covers the litter that creates a softer surface over the litter and gets peed on. This excess peed on hay is part of a normal litter box set up. Which is why it's preferred for most of us to not buy expensive pet store hay, but cheaper baled hay at the farm store(though still needs to be good quality), so it doesn't matter as much if a lot of it gets peed on and wasted.
https://rabbitsindoors.weebly.com/odor-free-home.html
Now, there is a chance you have one of those odd picky buns that doesn't like to eat hay from the litter box
If so, then you may need to provide a separate small hay box or bowl for your bun to eat hay out of.