Good news. You now know the problem. Sounds like discectomy is what you are talking about if the injection doesn't work. Herniation is likely not too bad if a discectomy is not first option. Either way good luck. I herniated and extruded disc fluid into spinal column on three discs and have tears in two - it is amazing how much punishment our bodies take. Also, when you head to pt keep in mind the dry needling to relieve muscle tension as you heal and begin to strengthen muscles.
Good luck, God's speed on the procedure and healing.