/diy/ - Do It Yourself

What's a good way to get rid of staining that's deep in some wood grain? I'm working on a guitar neck and some of the stain that I used on the front of the head stock has seeped down through the tuning peg holes onto the back. I've tried sanding it down, but it's in really deep. Pic related, I'm mainly concerned with getting rid of those lines near the holes at the top of the picture. Most of the other stuff should be covered by the tuners.