if it's blood in the semen sometimes a blood vessel will pop and cause that to happen
to play it safe see a Urologist.
When i masturbation for 4 years but after 6 month ago my penis is bleeding little not lot but i didn't go to see the doctor because i think i rub it clean with tissue paper and body lotion because it's stop bleeding and next last 1 month i went back again but i did't bleed that's why i take it easy and not go faster but don't it o.k?
You need to see a doctor immediately for this. Don't waste time on internet forums.