Well, you've just published 1 hub so far, so you most likely (nearly 100% sure) got rejected due to "Insufficient content". You should've gotten an e-mail stating the reason they denied your application.
If that is the case, I've read that most authors here agree that you need to write at least 10-15 quality hubs before they consider your site with enough content.
Oh, and yeah you can reapply pretty much anytime you want. If you sign in to your Adsense account you'll instantly see the page to resend your application. But I'd advise you to first publish at least 10 quality hubs before trying it again, that worked for me. ^^