Pain definitely is not in your head, nor is it exclusively in you’re tissue. It’s always real even in amputees with “phantom pain”. In fact, the more chronic the pain is the more it’s an output of your nervous system from a “Neuro tag”. This happens when a pain pathway becomes sensitized through repeated stimulation until it takes less & less noxious input to trigger the pain or “injured” response. Indeed the hurt you feel becomes the feeling you hurt.
Fortunately there are fairly simple treatments that are effective at normalizing these amplified pain responses. First is reassurance that your tissue is neither damaged or fragile even if it hurts. Then comes reactivation via exposure therapy whereby you “tune” your movements by finding the least painful way to perform fundamental tasks like tieing your shoes, kneeling to the floor or squatting from a chair. By following the credo if you want your body to feel better feel your body move better the threat of hurt equaling harm gradually dissipates & pain tolerance gradually returns to normal.
The most common belief is that something must be wrong in the body or damaged. This can be the case but the false positive rate for degenerative arthritis, disc herniations, narrow spinal canals, etc in asymptomatic people is often over 50%. So what this means is actually quite reassuring. That even if it is causing your pain you can adapt & live a highly functional life that is sustainable.