I felt like a little vibration kind of sensation in left lower abdomen area randomly when coughing hard. i don't feel any pain/bump. is it normal? because i feel concerned as i recently read online we may feel hernia in low abdomen when coughing?

Young adults become aware of bodily functions they never paid attention to before and must be reminded that if you must ask if something hurts or not, it doesn't. It is rare for a serious medical problem to exist at your age that doesn't cause clearly unpleasant symptoms. A small hernia may remain undetectable but isn't serious unless it traps bowel but then you'll have severe pain and vomiting