I have pain on the inner part of my thigh but there's no rash and no skin discoloration at all. i haven't made any lifestyle changes.

The most likely: cause is muscular. Pain from exercise including a muscle strain would top the list of possibilities. Other possibilities might be an inguinal hernia or pubis dysfunction, a condition related to relaxation of the pelvic ligaments. Causes unlikely in a 26 year old include osteoarthritis, sciatica, or kidney stones. You can watch it using ice/heat/ibuprofen for a week or two. Then see doc if persists