The symptoms you have described of having pain in left leg can have all kinds of different causes, as it is a symptom of many different diseases.It can be due to a torn or overstretched muscle (strain,a hairline crack in the bone (stress fracture,inflamed tendon (tendinitis). Other common causes are: Atherosclerosis that blocks blood flow in the arteries, deep vein thrombosis
), damage or disease of nerves/neuropathy.
You need following tests:
Electromyography(EMG) and nerve conduction studies
Arteriogram to check blood flow
Duplex Doppler/ultrasound of leg exam to look for a blood clot
The probable cause seem to be nerve root compression(pinched nerve)/neuropathy or inflammation. Take tab. Ibuprofen 400 mg from the counter. It is available as OTC(over the counter) without prescription & will help you greatly in pain relief.
So my best advise for you is to make an appointment with your doctor to have these tests done so as to know the exact underlying cause & then treatment will be done accordingly.