I have constant stiffness and pain in my left ankle. mostly in the morning and after driving for more than an hour.

Ankle pain: Did you hurt it when you were younger. Since you are young and it is localized please get an xray and let you doctor advise you what to do next.

Arthritis: You probably have some degree of arthritis in your ankle. You need to have it xrayed for starters. This will show the degree and extent of arthritis. You may feel better taking some anti-inflammatory medication if you are not allergic.