Plug your Iphone into your computer, launch up Itunes. Then cancel sync, wait to see if it automatically boots otherwise enter recovery mode, you could also enter DFU mode.
I have had this problem no ends of times after jailbreaking and this always sorts it out.
This updates to 6.1.3, which is not jailbreakable.
Should be able to put it in dfu mode and restore the the firmware that was on there before jailbreaking. After you restore the firmware jailbreak again. Also you could just put it in dfu mode and rerun the jailbreak. Also check for updated jailbreak software.
This updates to 6.1.3, which is not jailbreakable.
Grip iPhone tight. Launch onto concrete. Buy android.
Fixed.
I would, but there's more money in iOS development so I put up with it. Honestly when you get it working right, jailbroken iOS > Android