I had an epidural steroid injection at s1, and while inserting the needle i felt electricity shoot down my leg for half a second. i did not get a headache after the injection, but does the electrical feeling mean my dura was punctured?

To perceive an "electrical" sensation, the needle may have punctured your dura, and touched the spinal cord, but w/o a significant headache, it will heal quickly, and the steroids will suppress any inflammation. If a headache develops, see the physician who performed the epidural for what is called a "blood patch".

Possibly, the needle brushed against a nerve root in the cauda equina, but this could occur even if not dural puncture. Since it was transient and not lasting, there should be no persistent problem.