The first is to sue him in court to let the other party know that this thing is yours, not something he can use casually, and respect your patent right. Otherwise, whoever registers a patent in the future will always use it for others. It will cost a certain amount of money to register a patent and ask the other party to apologize publicly, compensate for mental damage, stop infringement and so on.
The second is to let the other party compensate for the loss. This is necessary. The other party used your patent. If it's pure misappropriation, that's fine. What if something happens? Do you want this patent or not? Who dares to use your patent in the future It doesn't matter where you say it. You have to ask the other party to compensate you for your losses during this time.
The third is to apply to the Patent Office for mediation. I don't think the problem is very big. You can take this step and let the Patent Administration help mediate without running back and forth. For example, cross-provincial infringement, this method can not be used. It is more difficult to defend rights. After all, it is difficult to implement across provinces.
The fourth is to send a lawyer's letter, which is also a warning letter of infringement. That is, if the other party is found to be infringing, a lawyer's letter will be sent to inform the other party that the product patent is infringing, and then the contact information of the patentee will be left to let the other party know how to contact and how to deal with the matter.
But the effect of sending a lawyer's letter is not very good. The other party may ignore it and replace or hide the products that have constituted infringement, which makes it very troublesome to collect evidence of infringement in the later stage. Therefore, it is recommended to use this method to collect evidence of infringement in advance before sending a lawyer's letter.