I think I can see it...? Maybe? Is it in the finish or in the wood? Can you tell how deep? If it's superficial, super glue makes a great filler/ hardener & can be coated with another finish, or simply polished once dry. If it's very deep/ into the wood, then the structural integrity has been compromised, and who knows? At that point, a glued-in biscuit/ dowel fix would be a good insurance policy.