I designed the product, but what if someone else applied for a patent?

According to the provisions of Article 45 of the Patent Law, any unit or individual may request the Patent Reexamination Board to declare the patent right invalid if it thinks that the grant of the patent right is not in conformity with the relevant provisions of this Law from the date when the patent administrative department of the State Council announces the grant of the patent right. You may file a request for invalidation with the Patent Reexamination Board, and issue relevant certification materials, and the Reexamination Board will make a ruling. If you are dissatisfied with the ruling, you can bring a lawsuit to the people's court.