Welcome to HCM
There are two possibilities for your pain
The first one that you might be having urine tract infection due to dehydrated kidneys plus there also might be chances of kidneys stones which if have caused hydronephrosis
makes the kidney palpable. urine analysis and ultrasound
KUB will be helpful
The second is you might be having lumbago
which degenerative disc chances in the lumbar and sacral vertebra which causes nerve compression and causes pain which radiates to lower limbs
For evaluation visit your doctor.