I've been having mild pain and some numbness on my left leg for about a week now. mostly around the knee and calf area. no swelling or other symptoms?

Disc herniation: You could possibly have a lumbar disc herniation which can cause "radiculopathy". This can present as pain, numbness or tingling from the back into the legs. A smaller disc herniation can usually be managed non-surgically. However, a larger disk herniation causing intractable pain and even weakness usually needs to be treated surgically. Would also consider weight loss.

Sciatica: Pain in the distribution as you suggested describes the pattern of the nerve that travels in the leg called the sciatic nerve. The sciatic nerve is not the cause of the pain source, it is the result of an irritated nerve typically in the lumbar spine (low back) which are caused by herniated disks, spinal stenosis or degenerative disc disease requiring further evaluation by a spine specialist.