L side herniated l5s1 disc now developing sciatica symptoms on right side why ? ( have sciatica on left side cortisone injec. 2/10/16 on l side)

Sacro-iliac joint: New "sciatica" opposite from herniation can be extension of herniation, neurogenic inflammation of the lowest lumbar discs, a piriformis syndrome or a sacro-iliac joint dysfunction secondary to overworking your right side attempting to protect left side. You need exam to try to pin down the specific cause and treat that cause!