Even though it is jailbroken, Apple still has to service it for any hardware issues. If you can reseat the LCD and digitizer cable, that may fix the issue. Otherwise it probably needs a new screen assembly. While you're at it, might as well fix the home button too while you're down there. But if it's in warranty, Apple should replace it for free unless it is clearly physically damaged.
Even though it is jailbroken, Apple still has to service it for any hardware issues. If you can reseat the LCD and digitizer cable, that may fix the issue. Otherwise it probably needs a new screen assembly. While you're at it, might as well fix the home button too while you're down there. But if it's in warranty, Apple should replace it for free unless it is clearly physically damaged.
Pat
iFix SB
http://about.me/ifix