I've had good luck with cheap hairspray helping to loosen the ink. That was on fabric though. The "solvent" in the hair spray is what breaks down the ink I believe. Aquanet. Cheaper is better. You want the aerosol spray not pump spray. Once its liquified you can blot up the ink. Be careful because you might end up spreading the ink more. I don't know how well hairspray might work on leather. It can possibly ruin the finish on the leather. I think you need to find a product specifically for removing ink from leather. Hopefully
@RaskyR1 chimes in. He's way more experienced than I.
Don't use magic erasers or other "household" cleaners like goo gone, wd-40, and so on. They will only damage the finish on the leather. Same with any type of ink eraser or other abrasive.
This stuff might be worth a shot. It's pretty cheap at $9:
http://www.autopia-carcare.com/leat...leProductSearch&utm_campaign=CSE#.VT4Qgrp--qQ
Here is another leather specific ink remover:
http://www.amazon.com/Leather-Maste...&qid=1430131085&sr=8-1&keywords=ltt+ink+stick