What do you suggest if i hit myself in the penis while it was erect?

If your penis : appears normal and does not hurt much, then you don't need to do anything. But if it is abnormally swollen, bent, or deeply bruised, you will need to see a urologist (or ER if late night), for evaluation to exclude penile fracture. You can also start a private message with a HealthTap doc and attach a picture if the injury is minor but you want reassurance.