If you've got a super tight piriformis, it's a good idea to try both stretching AND strengthening of that area.
These videos may be helpful:
If the sciatica is caused by muscular issues around the hip, you should be feeling better.
If not, you likely need some more personalized troubleshooting to get your spine balanced and unkinked. If you can find someone locally to help you, that would be your best bet.
If you can't, these videos may be helpful.