Pain in the back of the right side... the pain worsens after waking up

I've been experiencing persistent pain in my right side and back for a few days.
I'm especially curious whether it's due to my sleeping position or if there's another cause, as it feels worse after waking up.

It feels okay when I move, but when I lie still and then get up, it aches again.
I'm not sure if the pain in my right side and back is just a muscle strain or if I should also consider issues with my kidneys or internal organs.

Has anyone else experienced the same pain in the right side of their back?
Please share which hospital might be good to visit and how to manage it to improve. 🙏