Hairspray always works well on lifting ink out of things, but I wasn't sure if it would discolor the leather, so I did a search. From what I read, it works well. Here's what one lady said:
I put the hairspray on a q-tip and then went over the marks to avoid hurting too much of the leather. I let it sit for about 20 seconds and then in circular motions with a wet microfiber cloth I wiped it off, then I dried with a dry microfiber cloth and then wiped with a leather wipe to get the moisture back in. Amazingly it worked!
Also, another person recommended this:
Guardsman Store - Product Detail - Ink Remover for Finished Leather #374801
Good luck...hope this helps!