If you held in semen with your finger just before you ejaculate where does it go?

Blocked ejaculation: Usually the ejaculate and sperm travel backward and empty into the bladder. This is called retrograde ejaculation and is not harmful to you.

Retrograde: I'm surprised if you could do that succesfully - or why you would want to. Semen can go backwards through the urethra and into the bladder. This sometimes happens naturally, especially with diabetic men, and it's called retrograde ejaculation.