My ankle has an uncomfortable sensation but not painful enough to not exercise. i sprint on the spot 6 days a week, will this cause osteoarthritis?

Not likely: No, regular exercise, even sprinting should not cause arthritis in an ankle. Arthritis could be caused by a more severe injury such as an ankle fracture or repeated severe sprains.

Varies: It would be fairly unlikely that a 20 year old would have osteoarthritis in the ankle. I would not hesitate to be seen for an accurate diagnosis and to ensure you are not causing further problems by exercising on it.