I applied for a patent in China. What if someone else later copied it and applied for the same patent abroad?

Patents are regional, that is, patents are only valid in the country or region where they are granted.

If you don't apply for a patent abroad, it's considered that you didn't ask for protection abroad. This technology becomes public technology, and you can use it without paying others.

If a foreign businessman requests patent protection in a country or region where you have not requested protection and is authorized by law, then you have no reason to file a lawsuit and your lawsuit will not be supported.