The largest nerve in human body is the sciatic. It starts from the bottom of your back and runs through the buttock and down the lower limb. The sciatic pain is sometime occur by any sort of compression or irritation on the sciatic nerve.
This type of pain i.e. sciatic pain is not a disease or disorder, but it is considered as a symptom of another problem that is occurred inside your nerve. For example, a herniated disc, degenerative disc disease or a narrowing your spinal canal.
Sometimes this pains appears in the lower back, buttock, back of the thigh and/or calf, on the side of the foot, and in the heel. Sometimes you also feel numbness or weakness int these areas or a strange sensation like tingling or pins and needles.
This post shows how tennis ball therapy for sciatic nerve pains as well as back pain.
Watch this video that can help you.