Do you have a lesion on you penis? How is your injury? Are there blisters with fluid in it or there are pimples?
If you speak spanish you can ask me the questions in spanish.
If you have small fluid-filled blisters very itchy, the most likely cause is a herpes infection. Less likely could be a fungal infection.
The treatment for herpes is ZOVIRAX cream 5% (5 applications a day for 5-10 days)