Can i use pferde balsam(horse balsam) for lower back and sciatica pain?

No: Avoid it. It has no benefit anyway. Has the problem evaluated and then you will know how to best treat it.

Possibly: However, it will be temporary as it probably won't get deep enough to be next to the spine. Sounds like you have a pinched nerve in your back. I would suggest seeing a pain/spine specialist to evaluate you further to evaluate what level and what can be done to treat you. There are interventional treatments besides medications and surgeries that might reduce or eliminate the pain altogether