I'm just wondering if there's a way to fix the arm on a driver's side?

The most likely cause of this is the bolt that holds the arm rest in place has come loose and needs to be tightened.

There are a couple of different styles of this. If you have a zipper on the arm rest cover then you just unzip that, and the bolt will be accessed that way.

If not, then you will have a plastic cover that covers the bolt. Clearly this is the easiest way so hopefully you have this style.

Please see the attached info below and we can answer questions that you have about this.

If you have a different style, please get some pictures of what your arm rest looks like, and we can go from there.

Thanks