It means that most likely you are not infected. However, I have to tell you that NAT testing is not used to completely rule out HIV infection, because some (very few) infected people don't have any detectable HIV RNA. Serology test is the proper way to go, take that test after 3 months, as suggested by Teak above.
If a condom was used you don't need to test at all. Tell us in 3 months what your antibody test says.