By ablation, did they just "kill" the nerve? I assume that's what they did. Do you know what nerve it was?
If you're gettiing stinnging pain down the leg and into the foot I have to assume that the sciatic nerve is involved as that's the biggest nerve in the body and it runs all the way down the leg and into the foot. I'm wondering if he hit that nerve by mistake, or nicked it. If so, he could have aggravated it. This could take awhile to calm down. Pain meds many tiimes don't touch it if it's REALLY angry.
Best thing is ice (on the butt). Do NOT use heat as that causes more pain. Use ice for 20 minutes every 2 hours, and that will help to calm it down. You may need stronger pain meds too, but I doubt yoiu'll get them.
Just keep icing. I had sciatica (what that actually is that you're describing) for 26 years solid. The doc couldn't find a drug that would work and was afraid to give me a high enough dose to help. Just recently Ii got relief. (Thank God!)
I hope the ice helps you. It always did me for awhile. But never for good. God bless and take care. Hugs, Lee