Your dad should start on medicine Pantocid 40 mg 1 tablet empty stomach daily for 1 month. Along with this for now give him syrup mucaine gel 1 tea spoon 2 times a day for 5 days. Along with this pain homeopathic medicine Carbo veg 30 3 to 4 times a day and nux vomica 200 once daily.
Next Steps
if problem persists consult Gastroenterologist
Health Tips
avoid all kind of Spicy and non veg food. eat fiber rich proteinaceous diet and green leafy vegetables and fruits. do brisk exercise daily.