Pain in the lower limb can be due to many causes.It may be infective,traumatic,Vascualr etc.
As per your history,it may be vascular.Please consult your doctor and get Colour doppler of the Left lower limb to rule out Arterial disease like TAO(Thrombo Angitis Obliterans),venous disease
like varicose veins
If you are a smoker,please stop Smoking
Please change your position or move your legs regularly during office hours.
Another possibility is Musculo skeletal pain,which will be relieved with Muscle relaxants.
But,Please consult your doctor and get it checked.
Wish you good health.