“While accidents like these are frustrating, I promise that you don’t have to feel awful about them—especially since it’s easy to get the stains off with leather cleaner!
You can purchase leather cleaner from an automotive store or a retailer that carries automotive products.
If this doesn’t work, you might need to fess up to your dad, since he might want to consider taking the vehicle to a detailer. However, it sounds like he’s not the type to get upset about accidents, especially if you take the initiative to try and clean it up—so hopefully all will go well! (You can also tell your dad that in the future, he should consider using a leather protector on his seats, since this will help prevent any future staining.)
Good luck with cleaning; you’ve got this!”