You should get a dedicated macro.
If you are right for cash, you can get extension tubes, or if you have lens you dont care about, you can get adapters to mount your lens backwards on your camera to get the macro.
However, with these adapters, your F stop goes all the way whack. So if you do not have a fast lens, well, you are going to need a lot of light and you'll lose the depth of field.
Watch THE NIKON GUY on Youtube, he did a few videos on the extension tubes, very informative.
Nikon Pimp #82