I really wouldn't worry about it. With my first I was 2cm at 36w and went full term.
You can be dialated to a 1 for the rest of your pregnancy. Every pregnancy is different. I wouldn't worry, if it was a concern your doctor would have mentioned it. I think it is actually pretty normal beyond 30 weeks. I was dialated to a 2 with my last for many weeks, and I carried to term.