Hi, and thanks for your medical question on eHealth forum!
Pain in the upper left abdomen and chest area can be due to stomach issues (GERD or hiatal hernia), spleen issues, due to an abscess below the left diaphragm, a hematoma (localized collection of blood), an abscess, or a muscle pull.
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. Please discuss with your PCP. Hope this helps. Take care!