Upset stomach and tenderness in abdomen between ribcage. what could it be?

Variable: There are unfortunately numerous causes of "upset stomach" and "abdominal pain". These may include, but not limited to gastritis, ulcer, gallbladder disease, intestinal gas, gastric reflux, etc... It is best that you have a thorough examination and review of your symptoms by a family physician. This can help identify the cause or diagnosis and direct treatment. Be well.