Welcome to the Bunnings Workshop community. Thank you so much for joining us and sharing your question about how to fix a chip in your bathroom vanity.
I'm sorry to hear your vanity got damaged. I recommend using the PC-11 56g White Epoxy Paste it's a waterproof, non-toxic compound that can be sanded down once it has cured. Please note that the product will not be the same shade of white as your vanity. Clean the damaged area as best you can with an old toothbrush making sure that all the loose parts in it have been removed. Apply only what you need to cover the damage so that it will not be too noticeable. Use fine-grit sandpaper to smooth out the repair once the compound has hardened.
If you need further assistance, please let us know.