In a similar situation, I lit the area with a flood light and then took pictures without flash.

I have also zoomed in for a close up, rather than actually getting close to the area.

Have also deflected the flash, to prevent glare, with a piece of white paper.

If you want to show scratches, use a spotlight from an extreme angle. For example, if you position your camera perpendicular to the wood surface about 1 ft. away, position a light source at least 3 ft. from the camera, just above the wood surface. The extreme angle will cast shadows into the bottom of each scratch making it visible as a dark line.

You will get the best result if the spotlight is the only light source. Also, it's important to use a single point light source - such as a small LED or halogen bulb - don't use a multiple LED array (unless you add a diffusion filter) because the LED's will create multiple shadows in the scratches.