I just suddenly feel pain in the left side of my head, speciall when i touch it.

Depends on duration: If this persists or recurs frequently, you need to see your physician for an evaluation. There are local symptoms such as that which you describe that can be serious (as in a disease called temporal arteritis). If it is a single, transient occurrence and is not associated with other symptoms, and it subsides, don't pursue it unless it recurs.