I masturbated little vigorously by rubbing penis on bed, i've developed couple of tiny red dots on penis shaft, they do not itch or pain, should i worry?

Abrasions: Perhaps you need to add some lubrication like most men do. Dry friction without lubrication causes this problem and over time this can scar.

Don't Worry: You probably developed "petechiae, " due to minor hemorrhage of small capillary vessels under your skin, caused by physical trauma from masturbating too vigorously. They should resolve on their own. Consider using a water-based lubricant to reduce friction. Masturbation is normal and healthy, provided it does not become an obsession. Just treat your penis more gently; it's yours for life!