I receive a lot of queries concerning how to utilize yoga to relieve certains pains/tensions, specifically sciatica nerve pain, and neck tension/stiffness. I am not a doctor, nor a chiropractor nor a PT (but I have visited them all many many many many many times). That being said, below is a selection of links that I have found useful for my own self-care practice and perhaps they can benefit you.
Know that here is a plethoria of (good and bad) information out there, but first and foremost you have to see a doctor if the pain is chronic OR severe (indicating injury or damage).
There are yoga poses to strengthen muscles to help with joint problems like arthritis and stenosis, but remember that range of motion may be limited so you have to be VERY aware of your own body and not push (but also know WHEN to give a little more effort).
There are yoga poses to stretch the muscles around the sore area (if there is an issue with tight and/or overused muscles).
And there are poses that do a little bit of both.
There needs to be some good body awareness for any of the remedies to help: for neck issues posture can be a huge component. Notice, do you thrust your chin out when sitting at a desk or driving or walking? Do you walk hunched over with rounded shoulders and head hanging? Small postural adjustments will do you a world of good but you need to be aware of the issues first and be willing to make conscious corrections until the good habits take over for bad.
As for sciatica, the terms usually refers to pain along the sciatic nerve. This nerve runs out of the spine and down along the back of the pelvis to the back/side of the leg. It can go under, over or sometimes through the piriformis muscle, which means when that muscle contracts, it can press on the nerve.
Walking with the feet face out ("duck footed") is common when we lose our good posture and walking technique because the legs rotate OUT and this contracts the piriformis. Extreme sway back positions (lordosis) can strain the low spine and cause nerve discomfort. On the opposite note, the tail tucked under from squeeing the glutes can also compress the pirifomis.
Learning better techniques for posture, for standing, and especially walking properly, with the hips leading rather than the feet, or the chin, or shoulders, can help relieve strain on the neck, the low back and piriformis.
There are great stretches for the outer hips and low back too, but please know if your piriformis runs through the muscle rather than around it, some of the stretches might cause increased pain. For chronic pain and MRI might be helpful to determine appropriate course of action.
So, what is the bottom line? See a doctor if necessary - try different things, do really intentional self care, be aware of small changes, practice good posture, experiment a bit and don't give up. You'll find what works.