1. Is the joint solid? meaning no gaps?
2. live with it
3. fill over it with slightly thickened epoxy. this is easy if you plan to paint.
4. start over. ugh. I know how much work this is.
DO not sand wiht a power sander. use a cabinet scraper. or sanding block. power sanders will ruin the surrounding wood as the wood is soft, the epoxy in the joint is hard.
Thanks for your reply. The joint isn't great. I am leaving the joint until I start to cut out the planks from the panel. Then, if needs be I will either fill the dry area and sand or cut out the scarf along its natural diagonal and rescarf.