Refinishing the entire stock would be best, but you can use a Wipe-On polyurethane (like minwax from wally-world) to get it real close. Test it in a hidden spot to make sure it doesn't attack the factory finish or otherwise damage it!! Apply it thin with a lint free rag to the damaged spot, let dry thoroughly then smooth with fine paper, do this until it is perfectly smooth, but not glossy. For the final smooth / polish you need to get fingernail polishing boards, the ones that are sold in singles with foam centers (mine happen to be 6.75" x 0.75" from wally too). You probably only need 'Conditioning' and 'Shine' ones, but remember all the other grits for future projects. Then go over the area with the condition first then the shine and it should Gloss up pretty well.