Could it still be covered under warranty.

If you're not trying to repair it, and just want to reinforce it so it doesnt tear more...

Cut off a small piece of material...maybe something like denim, and tuck it inside the tear. Work it in there with a toothpick or something similar, to make sure it's laying flat. Make sure to over-lap all around the tear, inside the seat...especially at the corners where the tear would extend.

Use a glue (something like gorilla glue or Loctite), and put it on the new material....gluing the inserted material to the cut leather. All glue is between the new inserted piece, and your seat leather. You can use superglue, but if you arent perfect, it'll be noticeable on the outside, whereas the other two allow you to wipe it off before it dries.

Hold the seam together, so it dries without being open...you can even use some masking tape, or paint tape to hold it overnight while it dries.

This should keep it from tearing worse.