If you use your meter before you eat and 2 hours after first bite, you can judge for yourself whether that food harmed your blood sugars. It will help you gain control of this condition, which has to be better than a few sore fingers.
If your fingers are very sore, are you using the lancet properly? There are different depth settings and maybe you are using the wrong on, and also do you stab your finger at the side or at the tips? Most people find stabbing the tips hurts more. Personally, I don't.