i broke a blood vessel on the top-behind side of my penis.a lot of blood came out but now bleeding stop..but the the vessel is extending little bit apart a the point of cut..it hurts..now what should i do???
Blood vessels are under the skin, you'd have a contusion (bruise) where it was torn. Did the skin itself tear?
Look up frenulum. From your description this is what I think you're seeing. The frenulum tore, it can happen during sex or masturbation. Yes, it will bleed heavily. It may/may not reattach. It can tear again.
You might consider seeing a urologist for an exam.