How to fix my zoom on my Nikon 14-24mm

First of all, do not attempt to force the zoom ring to turn. Doing so will only potentially lead to breaking more components in the lens.

From my experience, stuck zoom assemblies usually are caused by a loose screw or something getting stuck, or some part of the zoom assembly breaking and jamming things up. The way to go about fixing it would be to just start taking apart the lens and try to look for whatever is stuck in there or is causing things to jam up.

The zoom assembly itself is usually made up of a couple lens barrels with screws going through the side of it to hold in a series of lens elements. The side of the barrels will also have curved and/or straight slots allowing the lenses to move. When you zoom in and out, these lenses are designed to move in specific ways.

It's usually best to avoid disassembling the zoom assembly if at all possible. Obviously since the issue is with the zoom, there is a fair chance you could end up having to disassemble it, but sometimes the issue doesn't lie within that assembly, or can be fixed without disassembling it (such as if there is just a small screw that you need to pull out of it). The reason to avoid disassembling it if possible is that it's a complex assembly, it has lots of screws and parts, there are several lenses that you have to be careful about not getting dirty, and the outside of the barrels are greased (and the more you handle the barrels, the more grease you will rub off of them). Below is a couple of zoom assemblies I had lying around to give you an example of what to expect.

If you do attempt the repair on your own, definitely try to see if you can find a parts list for the lens. Parts list shows exploded views of the lens and shows you where each and every part goes. It can be an extremely useful resource. I did find this guide, which shows you how to take apart a portion of the lens. You might also be able to find additional guides online.

With what that lens is worth, it could also be worth considering sending it into a repair shop. It just depends on how much the lens is worth to you and if you're willing to pay for repairs (which would be cheaper than buying a replacement). I mention this because I'm assuming you haven't worked on camera lenses before. Even if you have experience with other electronics, camera lenses can be complex. If you do manage to repair the issue, there is a real risk that that you accidentally damage something else while making that repair.