Obviously nobody can diagnose injuries based on Lemmy comments. My advice is to find a good physical therapist. I found one who specializes in my sport (powerlifting) and he fixed a nagging injury I'd had for years.

Hot packs might help discomfort but they won't help heal anything. Warming up is certainly important. Stretching could be important but the hard part is figuring out what you specifically need to stretch, which is where a physical therapist can help.