My camera fell while on the tripod and the lens fell off completely while the camera body remained on the tripod so when I reattached the lens it wouldn't stay it works and everything but I just have to hold it together. Should I try to take it to a camera shop or just send the lens back to Nikon so I can get a new one ?
There may be a problem with the lens, but it is more likely that the lens mount on the body has been damaged. You need to have either a local camera shop or a Nikon service center look at both the lens and the camera body.
Some things that will affect your decision:
What body and what lens are we discussing? If it is an older entry level body and a relatively inexpensive lens, the repair by Nikon may actually cost more than the camera or lens is worth.
Is your equipment still under warranty? Even if under warranty, Nikon may or may not cover damage from a fall on a tripod.
If you know anyone else with some Nikon gear, try using a different lens and another camera body with your camera and lens to see which component is the source of the problem.