Here's a video that might help - https://www.youtube.com/watch?v=a-OyxRQgrG8
You can use filler or replace a board. Here's an article that explains it:
Minwax stain markers for surface scratches. Minwax Blend Fil pencils for deeper scratches. Minwax wood putty for real deep scratches and gouges. Come in all wood tones.