(2) Pain can be from something as simple as underusing a region of muscles. Once you know your specific problems it's often really easy to treat and prevent.
(3) Fixing that sooner rather than later is probably a good idea. You heal faster when you're younger, and chronic pain can easily become a mental pattern long after the physical trigger has healed (and AFAICT psychological therapies for that sort of pain are still in their infancy).
(4) Muscles and bones benefit from impact, even something as mild as walking 10-60min daily. If you're physically atypical in any sense then still see a doctor to make a plan first, but adding a little of any sort of exercise will probably help mitigate any issues.
(5) Reiterating, if you're currently in pain, see a professional.