Hi and thanks for the query, it shall be worth while knowing whether you engaged yourself in an intense activity, or a physical activity you are nor used to lately. This could simply be a mechanical pain. The pain onset, whether very acute or gradual or of fundamental importance. Accompanying symptoms like fever, cough, fatigue are important to exclude an infectious origin. A physical examination shall be required to determine any costovertebral angle or abdominal tenderness. A urine test might be required to exclude urogenital causes of side pain like renal colic. An abdominal ultrasound could be needed at some point during the evaluation process. I suggest you take an appointment with your primary care physician for a proper evaluation. Thanks and best regards, Luchuo, MD.