Pain under the left shoulder blade is usually a referred pain
from abdomen like stomach
ulcers, acidity, pancreatitis, or ectopic pregnancy or from the chest like in heart attack, pericarditis, pleuritis, pneumonia, pulmonary embolus, and aortic dissection. Since the pain is not much chances of chest related causes are less. It is in all probability acidity due to medications you took.
Raise head end of bed. Take Omeprazole empty stomach in morning and an antacid gel at bedtime.