hi sir/mam,its purely muscle related and in no way connected to kidney.pain that aggravates on straining like cough,sneeze is mostly due to intervertebral disc(lumbar or thoracic)pathology like disc prolapse,disc swelling,degenerative diseases.due to the above causes,the paraspinal muscles go into spasm when vertebral strain occurs as a protective reflex.you might be having pain even when you raise your leg without bending the knee in supine position(when you lie on your back).i usually recommend my patients the following:
1)rest for atleast 4-5 days.
2)completely avoid lifting heavy weights,strenous exercises.
3)tab.aceclofenac or ibuprofen with chlorzoxazone twice daily for 4-5 days would relieve you from pain.if you have any kidney issues,avoid above drugs and can take tramadol with paracetamol or acetaminophen.
4)as it may cause gastric irritation,tab.pantoprazole once daily before food is recommended.
5)after pain relief,phsiotherapist can guide you regarding back muscles streghtening exercises.
a thorough examination by an orthopedic surgeon to rule out other abnormalities like scoliosis spine cant be overlooked.so,whenever possible,please go for a consultation and have your MRI spine done.hope my answer helps you to get rid of your symptoms.any other health issues,please let me know.it would be my pleasure to assist you.thank you.take care.bye.