I have a bad pain on left side right below ribs. Its just a ache but extremely hurts when I cough. What could it be? Will it go away without goin to doctor?

Could be many things. It's hard to know exactly where the pain is coming from without an exam... could be from your intestines or other internal organs, could be a muscle spasm, could be your lungs. I suggest getting seen by a doctor if it is continuing for another day or so. Sooner if it's getting worse or if you get a fever, worse cough, or vomiting. Good luck!
Pleuritis of the. left lung is probably the cause. It could be also be pneumonia or Tietze's syndrome among other causes. Otc antitussive cough medications and nsaid drugs would help. See your doctor . May need a chest x-ray.