Pain is an output from the brain when it senses danger. It is like a smoke alarm it doesnt know if the toast is burning or the whole house is on fire. Also, past experiences affect pain output. It is real.
Pain comes from mechanical or chemical irritation, and an overactive nervous system.
Once tissue is healed and pathology is ruled out pain may persist for several reasons. The good news is the brain is plastic and can be retrained not to send out a pain signal. Neuroplasticity.
Neuromatrix of pain explains this well. Google those terms and see if they help your understanding of pain. This is not an easy journey but is winnable. And as much as some dont like it...movement is key. Gentle easy movements within the pain free or easily tolerable range, say 1-2/10.
Be easy with yourself. Knowledge is power and you have the power to change a lot of pain issues once pathology has been ruled out.
Peace\
Bob