One, circumcision doesn't really have anything to do with nicking your penis. It wouldn't have hurt any less if you had foreskin.

Two, genitals are extremely veinous: there's a ton of blood vessels concentrated in a small area, so even a tiny cut bleeds a lot, like your forehead. You'll see a lot of blood and the cut will open easily, but you're not in any real danger.

Use a topical agent like Neosporin to promote blood clotting and bandage it as best you can. Clean it and reapply the bandage regularly to avoid infection.

And maybe look into laser hair removal if this bothers you that much.