I was quite young at the time but as I recall, I just waited for a minute and eventually it starting trickling out. For as long as I can remember, I would get so excited about peeing outside that my penis would get partially hard and I would have a hard time peeing.
One of the earliest things I can remember is my mom taking me pee in an outhouse, and holding my penis towards the urinal. I can remember just positively not being able to pee even though I needed to... eventually wound up peeing on a bush on the trip home.