Longer ago than I care to admit I lifted what I thought was a costume flight case out of a truck during a get in (I forget which show) it had been mislabelled and was in fact a Dimmerrack, I never found out the weight but given the flight case was as tall as it was it must have been 150kg.
My lifting partner got off light but the sensation I felt in my back was hot, and cold and like a fistful of elastic bands being pulled past their elastic limit.
I was off for weeks and it wasn’t til much later I found out I had Herniated the disc in my lower back, ever since with increasing regularity something will twist and the bulge will pop out again and pinch that sciatic nerve. I have never felt pain like it, It will make me weep all over from the sheer exhaustion as much as the pain.
Everyone else’s tips are all the same I would offer, keep as mobile as you possible can and DO NOT just lie in bed (not that that is any more comfy for me anyway). I find for me that heat and/or baths for the relief they offer just make me feel worse later, but it worth a try. When it has been truly dreadful I have had IV painkillers, and diazepam, and they work exceptionally well, however eventually you have to stop taking them. NSAIDS and paracetamol and codeine help me most of the time, finding some stretches, trying to move as much as you are comfortable, and as stupid as it sounds relaxing during breaks as much as possible so that the spasms don’t draw your muscles into stupid positions which then ache or fail to protect you from twisting another way.
When it comes to such pain I have no qualms about suggesting speaking to your doctor and getting what painkillers you can, the pain can be excrutiating and its not something you can just “suffer through” until it goes away, it will do more damage ion the long run.
All the best @Sikamikanico