What is the difference/similarity/benefit/purpose/meaning/etc of pain, soreness, opening, and injury?
The purpose of yoga is to overcome unnecessary pain - physical and psychological pain - and to become indifferent to it as it arises. Yoga is a means by which we learn to navigate our life and our bodies differently - so that we stop doing that which causes us to suffer. Whether these are mental patterns or physical symptoms - only we have the power to change them. Thankfully yoga provides us with many tools to achieve this.