Hi
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Sharp stabbing pain under left ribs could be due to acidity with gastric reflux or hiatal hernia. Take a late night snack. Raise head end of bed. Take Omeprazole empty stomach in morning and an antacid gel at bedtime. Refrain from smoking, alcohol, fuzzy drinks and spicy food. Walking around also helps clear gas. I would strongly recommend you to see a gastroenterologist (a specialist who looks after the diseases of our digestive system) if these tips help you. Other than that it could also be costochondritis, pleuritis (inflammation of covering of lung) or pericarditis (inflammation of covering of heart). Since you do not mention any other symptoms, it is less likely to be any of these. IBS, Crohn’s, chronic constipation, spleen problems like bleeding, cyst, abscess etc can also cause pain under left ribs.
Since I cannot examine you and know other related conditions you may be having, nor is a detailed history possible on net, I have listed the various possibilities that should be looked into. Please consult your PCP for primary examination followed by proper referral. Take care!
if you're still having this problem, see a doctor asap. good rule of thumb when pain is severe.