Muy left leg has had a burning sensation for about a week now , from top right to my toes and it seems to be getting stronger, what could be cause?

Burning: Sensations like burning and tingling can be a sign of undiagnosed diabetes or another nerve damaging condition. If you haven't been thoroughly evaluated by your podiatrist or neurologist, you should schedule an appointment right away.

Lumbar spine: Burning pain which radiates down the leg to the toes is commonly due to irritation of the lumbar nerves as they exit the spine. This could be due to a bulging or ruptured disc or just local muscle spasm. Check with your pcp for a referral to an orthopedist or spine specialist. You will likely need lumbar x-rays and possibly an MRI if it persists.