What could be the cause of pain in my left leg only?

More info needed. So many things can cause leg pain that more information is really needed to give you a good answer. Any redness-maybe infection; swelling-maybe bloodclot, or varicose veins; injury/trauma-maybe muscle or bone problem;warmth-maybe gout or other kind of arthritis. And i really haven't begun to list everything. So, if the pain is bad or limiting your function, be seen to get a better answer.Good luck.