I was mastirbating yesterday and when i ejaculated blood came out. should i be worried and see a doctor soon?

Get examined: Although blood in the semen (hematospermia) is usually benign and resolves on its own there may be pathological causes. The most common cause is prostate biopsy. Other possible causes are infections, tumors, anatomical abnormalities, stones, or inflammation in the genitourinary system. I therefore encourage you to go to a medical clinic to be properly examined with routine lab studies.

Contused or bruised: the ducts carrying semen to the penis during masturbation is probably the cause. I would say see a doctor soon rather than late .

See a urologist: Anytime a young person has blood in urine or semen cancer has to be excluded. See a urologist asap.

I say no: This happens to most young guys at one time or another. A little vein broke from all that pressure. It is essentially never serious. Get seen if it lasts two weeks or more.