Ice packs for 3 days. The muscles tighten up to protect the back.
I can’t remember the name of the treatment, but my doctor strapped me to a table and put harnesses above anf below the affected disc. Then it used micro pulls to restore tge spacing between the discs. This was 30 minutes a day for 30 days straight.
That worked for me.
He also prescribed muscle relaxers but I rarely used them and only as a last resort
Also use all the stretching exercises described by the others.
Get a good firm pillow and learn to sleep with it. Put it under your legs when you’re on your back and between your legs when you’re on your side. This takes getting used to but I’ve been doing it for 45 years.
If 1 pillow isn’t enough, then stuff another in the same pillow case.
I also have a top of the line matress/bed that allows me to elevate the feet and head.
Getting the pressure/strain off your back is the key