You need to post more information. Can you boot into recovery? If not, have you tried to boot into download mode? If you can get into recovery, mount your usb in recovery, flash a nandroid (backup) to get your phone working again. If you do not have a backup, connect your phone to your computer, mount your usb in recovery and trasnfer a rom to your phone and flash it.
If you cannot get into recovery, I would download Odin and the NG2 tar file. Boot into download mode and Odin the tar file to get back to stock. I want to say I have seen a few experimental tar files on here. This is what I would do, no guarantees.
I do not mean to kick you while you are down but if you do not know what you are doing, don't do it. You have to read read read and read some more before you do any of this.