Well, under these circumstances, with no prior history of bleeding problems, urinating problems, etc...there is no doubt he is been traumatized. Here's the problem:
The penis is very vascular and if she pulls away it can really twist and damage his penile sheath. So, with obvious bleeding present, there is no question, he really needs to see a vet to get appropriate pain medication, anti-inflammatory treatment, and an examination of the penis to ensure no severe trauma and isolate where the bleeding is coming from.
Well worth an ER trip in my opinion.