It can be Renal stone or stone blocked in the left ureter
Please get an Ultrasound
abdomen for proper diagnosis.
If it is normal,then it could be musculo skeletal pain.
Till ultrasound,you can take Antibiotic like Norfloxacin
,Antispasmodic like Dicyclomine
and anti inflammatory drug.
Drink plenty of liquids.
If you come back with Ultrasound report,i will clarify further
Wish you speedy recovery