Increase the ISO
When it comes to exposure settings, the limiting factor is usually aperture choice. Lenses have a fixed range of apertures and when you’re shooting in low light conditions you may not be able to open the aperture wide enough to let enough light into the camera to achieve rapid, action-stopping shutter speeds. This is where the adjustable ISO setting comes into its own. By increasing the ISO, you essentially turn up the volume on the sensor, amplifying the signal (light, in our case) so that an image is formed with less available light. The drawback is increased noise, fewer fine details and a colour shift, although Nikon cameras are renowned for their high ISO performance and you’re unlikely to suffer any real image degradation below ISO6400.
You can change the ISO manually between shots, but why not try using your camera’s Auto ISO function? Here, the camera will automatically adjust the ISO up to a maximum sensitivity that you’ve preselected. It works surprisingly well when you’re shooting in manual exposure mode: you can set your preferred combination of shutter speed and aperture and the camera will choose the ISO that will deliver the best exposure, according to its meter reading. It’s a fast way of working, particularly in low light conditions.