The area you have described is medically termed as left hypochondrium and the pain in this area can be felt due to number of causes.
Most common of them are: colonic diseases or splenic diseases,irritable bowel syndrome,spleenomegaly(enlarged spleen).
Also it can be due to kidney stone.
You need urine examination,blood work & an ultrasound to know the underlying cause.So I suggest you to see your doctor soon.
Hope my answer had helped you.
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