I hit my left ear and now it hurts when i burp or hiccup. is it absolutely necessary for me to go see a doctor and what will happen if i leave it alon?

Possible perforation: You most likely irritated your ear canal and/or tympanic membrane. When you burp or hiccup you valsalva which increases pressure in your eustachian tubes, and may increase pain to irritated ear. There is a small chance that you could have perforated your tympanic membrane. If any blood or discharge or decreased hearing, see a clinician asap. Otherwise, try tylenol (acetaminophen) or ibuprofen.