I don't think it is a problem. After you get approval from Adsense you can put your code to any site (You own or you administrate ) as long as that site not violate TOS.
its your adsense account that matters not your url..just make sure your new url is not against their policy.
don't worry abt that. i approved with one website. and that website expired .. am using adsense account with another website. and still working fine. once your account approved adsense you can use adsense any where