Carefully massage the knot out. You can use the corner of something and lean into it. Be very careful especially if it's near your spine. Start gently. Foam rolling can also help but look up how to do it properly. Then sleep on your side with a pillow between your legs to help keep your back in a good position through the night.
I dunno much tbh. But I know you should have good back muscles to prevent backpain at older ages. My dad was very happy about how his back has no pain even at old ages because he worked it in construction
Even as a yank, I feel embarrassed that I never listened to my gut instinct in the first place. If I did, I could have told you that Trump would have won months ago but I was still uncertain calling it going into election night