Well, that sounds painful. Is it better? Did the violent or traumatic injury happen because you solidly erect? https://www.medicalnewstoday.com/articles/320963 That link is about bruises to the penis. I'd think that if you are recovering from an injury, you may want to hold off from sex altogether let alone with viagra. Was this your normal doctor or a clinic/urgent care/ emergency department?
I don't understand. Is your problem you can't get an erection? Or is your problem you believe you have an injury? Viagra would only be suggested if you can't get an erection, depending on your age. If you're a young man, I don't think that would be suggested, but you don't say how old you are. If you are just irritated down there because you took a very sensitive part of your body and treated it badly, that will just take time to heal. Again, not sure what the problem is because you didn't say.