I'm sorry to hear about your brother's pain. I have a herniated disk in my neck that is from an injury I got in my 30s. If it's the disk, he might end up needing an MRI as well. Sometimes they want physical therapy tried before doing an MRI. To me the herniated disk feels different from something like muscle pain because it has like electrical pulses, it's very distinct feeling.
My treatment started out with prednisone, then about 8 years ago I was able to get physical therapy. Since then, any time I have a flare up, I consume large amounts of cherries, fresh or frozen are best, like 1-2 cups a day. Sweet cherries work as a natural COX-2 inhibitor similar to ibuprofen. This is why cherries are used to treat gout and arthritis. I generally feel relief at day 2 but I eat them for a full 10 days just like I would with prednisone. I do not know of any negative side effects, it's something he could try while waiting for the Dr.
It might be a pulled muscle instead of a herniated disk. With a herniated disk ice can help reduce inflammation, but for muscle spasms heat is often more relieving and ice can actually trigger a spasm. Hot baths with epsom salt can help relieve muscle pain. Aspercreme has an OTC lidocaine cream that can help muscle pain as well
I hope your brother feels better soon!
unpleasent for sure, but not the worst I've had and it is localized to a single nerve