Yesterday i hit the left side of my head, it hurt for 2 minutes. today it only hurts when i touch it. how can i know there is no internal bleeding?

Definite-imaging: If you want a definitive answer then you would want to have imaging. However, not all traumas will need that. I am wondering why you are concerned about possible bleeding. Did you loose conciousness ? Are you having severe symptoms or nausea, or sleepiness? or bleeding? If yes, then you definitely need to be checked out in the hospital. If infected also need hospital.