Stuck in clockwork mod

[macbully]

Hi, there,

I was unrooting my nexus s to send in for repair, when my nexus s just got stuck.

Every time I turn on the phone or reboot it, it just goes to the Clockworkmod recovery screen.:-\

If I try to install any ROM it gives me status 7 code.:'(

How do I fix this?

Any help would greatly be appreciated.

Thanks