Hello Asimjavid.
Many thanks for your response. Yes, I am a physically active person. The strange thing is that although my left side is higher, I feel a deep aching pain in my right side. I am right handed by the way.
I have been doing a lot of foam rolling in my upper back which seems to help with the tightness and soreness.
If there is nothing obvious that can be seen in my photographs then I think the best course of action is to keep up with the foam rolling and stretching and wait to see a physiotherapist when the lockdown is over.
Best regards.