Hello According to your query this type of pain may be due to these reasons , these includes. 1 Renal calculus , diagnosis can be confirmed by ultrasound of both kidneys with emphasis over left kidney. 2 The next possibility may be due to amoebic colitis ( particularly in summer season ) . Diagnosis can be confirmed by stool examination for entamoeba histolica . In this case physical examination is also very important . 3 Hyper acidity may be the one more cause ,but in your case this is a least possible cause. In my opinion consult a physician and get his opinion as physical examination is very important. Rantac i.e ranitidine is antacid tablet and provide symptomatic relief, while nicip i.e nemuselide is a pain killer but this also produces hyper acidity.So the best option is to consult a physician and get his opinion. Good luck.