My son got a ball-point pen mark on the back seat. It is about 2 inches long in blue.
How can I remove it safely from leather?

Try Isopropyl Alcohol to remove ink from leather. I have also heard that the Mr. Clean Magic Eraser works wonders as well.

My wife swears by that Mr. Clean Magic Eraser... it can do anything according to her.

I have successfully used hair spray to remove ball point pen ink. For leather, you might try spraying it on a rag, then rubbing the spot. Best to test whatever you want to try on an inconspicuous place, like on the rear seat bench where it tucks under the backrest.

Leather cleaner worked for me before if the ink hasn't been there long.

Mr. Clean Magic Eraser!! It'* awesome and it won't harm your leather. I use it for everything, the car, the bathroom, kitchen, walls, you name it. Just dont use the same 1 eraser for everything lmao.

I would do the magic eraser, then leather conditioner.

A tad off topic, but will the magic eraser dry out the leather? My mom brought up this point after I used one to completely clean all my leather in my car.