You own a monopoly in your design. Your registered design gives you the right to take legal action to prevent other people exploiting a product identical or similar to that registered, without your consent.
You do not need to prove copying. You can use your registered design to prevent another person from producing a product that looks identical or similar to your own even if they have never even seen your product before.
You can indicate on the product and related literature or packaging the fact that a registered design has been obtained and the registered design number. This official notification acts as a worthwhile deterrent against potential copiers and demonstrates to others an intention to enforce your intellectual property rights.