How were physical ailments, such as severe lower back pain, dealt with by ancient hunter-gatherer societies?

I study the American Southeast, particularly hunter-gatherer groups in the period before the development of agriculture / domestication and permanent settlements.

At least in the region that I study, it's difficult to know exactly what people did for chronic ailments. Although there are natural sources of things like salicylic acid, which can be found in (among other things) willow bark, these would not necessarily have been available in high enough concentrations to really have much of an effect on people's long-term, chronic pain. They might have helped a little, but they were hardly the ancient world's equivalent of aspirin in terms of effectiveness. The process simply wasn't there to obtain dosages like we can get today from a couple aspirin.

And whether or not they had access to those things, we know that people suffered some incredibly painful long-term degenerative diseases from skeletal remains. Fractures that were not properly immobilized or stabilized when they healed on occasion resulted in measured differences in the lengths of limbs.

We see examples of long-term arthritic osteophytic growth in joints, and in vertebral columns.

We also see examples, especially in some fairly ancient hunter-gatherer populations, such as at the Windover site in Florida (ca. 6000 to 8000 years ago), of severely worn teeth. "Worn" as in, pretty much down to the gumline, and sometimes some fairly hideous dental abscesses. In some cases, these abscesses probably caused death, but in the lead-up to death, they would have been exceptionally painful. Especially among hunter-gatherers, the coarse diets people ate were enormously damaging to teeth, and even folks in their 30s and 40s were coping with some seriously worn teeth, and probably a fair amount of pain from that.

We also see people healing from some fairly severe traumas, up to and including violent conflict. One case at Windover that I recall was a male (age I don't remember) with multiple healed (but not fully mended) rib fractures that suggested severe impacts to the rib cage. The breaks were healed, but several of the ribs had not actually fully re-joined, and that would likely have been, at minimum, very irritating, and probably painful for as long as that person lived.

Another Windover case of particular interest was a kid, roughly 15 or 16 at the time of death, who had spina bifida, a condition where (among other things) the vertebra don't fully fuse, leaving the spinal cord partially exposed. The condition causes severe disability, but the kid survived into his mid teen years. He also had a leg that had essentially rotted away. He would have lived with this condition from birth. That's a really painful 15 years of life.

It's really hard to know exactly what people would have done about these things in terms of dealing with the pain, and like I said, there were certainly natural remedies that might have helped ease things slightly. But not even (most likely) to the degree that modern aspirin or ibuprofen provide. In general, it seems likely that people often just had to suffer with these things. Sometimes, based on the amount of osteophytic growth we see, or on the degree of tooth wear, it appears that they may have suffered for years from some of these conditions.

People in the past, not only in a hunter gatherer societies but also in pre-agricultural and agricultural societies, probably had higher thresholds of pain just from dealing with chronic low levels (or higher) of pain from various physical ailments all of their lives.

Honestly, if you were going to travel in time back to one of these societies and wanted to know something to take along with you to help you fit in, the best thing would just be to take along with you a long-term supply of basic over-the-counter analgesics. Just the effects of a couple of Aleve for a significant segment of many ancient societies would have been enough to make you a very popular person.