Try steaming it out. Take a small piece of paper towel and fold it a few times and moisten. Then press the tip of a soldering iron right over the ding (with the paper towel between the iron and the neck). If 2 or 3 attempts do not produce results, prop the bass sideways so the ding is vertical and place a very small but damp piece of paper towel directly on the ding. Leave it there for a few hours and see if there is any improvement.
If not, have a competent tech fill the ding with superglue or thickened lacquer.
I remember this technique. It really works; my ding was the result of my oaf-like tendencies