Hello and welcome to HCM,
The symptoms of pain in the left waist region after sleeping in a particular posture suggests soft tissue injury
Soft tissue injury can cause pain, internal bleeding
, hematoma formation.
You can take analgesic
(pain killer), rest, and hot fomentation for symptomatic relief.
A topical application of analgesic and serratiopeptidase
preparation can help to relieve pain.
However, a X-ray of the abdomen is required to look for the extent of soft tissue injury and / or bony injury.
Consult your doctor for a clinical examination, investigation and thus management.
Thanks and take care
Dr Shailja P Wahal