Syatic Nerve

I was injured in a cheerleading accident when another person fell from the stunt and landed in the pocket of my lunge, putting my leg out of joint.
This injury occurred over 10 years ago and for the past two years I have been experiencing problems with my leg continually popping out of joint. Now it has progressed to what has been described to me by a nurse as a pinched syatic nerve.
When I am working, lifting, walking, or just sitting on the couch, I get a sharp piercing pain in the middle of my right butt cheek that feels as though someone is stabbing an ice pick straight into my cheek and it travels down my leg.
When this happens, I cannot put weight on my leg or sometimes it draws my leg until I cannot even stand on it.
When it locks up, all that I can do is bear it until the pain passes.
I used to see a chiropractor years ago for a whiplash I received in an automobile accident, until the whiplash was corrected between another accident and treatment. Other than seeking treatment, is there anything that I can do to ease, or fix the problem.
I was wondering if there is any stretching or exercise that will help with the leg going out of joint and the piercing pain in my leg and butt cheek. Any suggestions you can offer will be much appreciated.
Thank you so much.