Use Dynamic Porcelain repair. The first step is to make sure all the dust is removed and that there are no loose pieces of porcelain. Then, take the appropriate colour of this heavy bodied paint and squeeze into the affected area until the hole is full. Don't over apply either Porcelain repair or Appliance Touch up with the thought that you can easily sand off the excess. These paints are very tough and durable so sanding is only intended for the fine finish step. You may need to repeat depending on the depth and size of the repair area.