Now that you have the land certificate, it proves that you have the right to use the land. Then, did you apply for a "building permit" before building a house?
I suggest you go to the Housing Authority for enquiry and handling. Basically, you need the following procedures-
1, self-built building permit;
2. Land certificate for self-built houses;
3. My ID card and household registration book;
4. If you can handle it, you must also pay deed tax and stamp duty;
Hope to adopt