Velvet is such a nice fabric, especially for a dress, and may need special care if you want to keep it in good shape for a long time. If you’ve already tried to clean it with water, you may have noticed that the fuzziness got stuck in a new position. And most of the time, you can’t undo it. It may be better to ask for a professional cleaner for soft fabrics.
They will probably wash it with a special brush that’s suitable for this type of material. Don’t worry because it will look as good as new.