This is a bit odd, the 720 should take some decent images in lowlight given that it does have a f1.9 aperture, it'll be obviously a bit less sharp because of such a large aperture and low megapixel count.
Anyways I'm probably boring you with this stuff...
Go into Nokia Camera and check out the tutorials built into the application, you'll learn how to adjust ISO, shutter speed and exposure so that you can get much better lowlight images.
With the right tweaking on Nokia Camera, even a Lumia 520 can take impressive lowlight photos.