Now, Now. You have to be patient. The Supporters and Moderators of this forum aren't on here all the time. It's done on a purely volunteer basis, so of course you can't expect an instant answer.
I will attempt to answer your question.
Everyone is different. There are people whose penises grow first, some whose penises don't grow 'til they're 19. Some males don't hit puberty 'til they're 18, some hit puberty when they're 8. You're unique, and you have to accept that. So, just because you have a small penis now, doesn't necessarily mean it's going to stay that small. Be patient. Besides, you're 13: you have tons of time, and the size of your erection shouldn't be a huge deal for you anyways. Just embrace how your body is growing, and try to be as healthy as possible.