Patents are regional. China's patent is only valid in China, and South Korea's patent is only valid in South Korea. Checking related patented products in Korea does not infringe your patent in China, but they sell products made in Korea to China, which infringes your patent. You can ask the intellectual property office where the domestic buyer of the product is located to handle it or bring a lawsuit to the court, or you can ask the customs of the imported product to detain and prosecute it.
If you are satisfied with the above opinions, please adopt them.