Pain in the side of abdomen is called flank pain. Usually flank pain is due to kidney stones. Ultrasound of abdomen should be done to rule this out.
Other than this it can be due to a muscle pull or due to an irritated nerve. At times it is due to gas, cyst in ovary or due to appendicitis.
It is difficult to diagnose this on net.
Please consult your PCP for primary examination followed by proper referral.