You have two options;
The first is the easiest. First back up your phone. Then go to Settings > General > Reset and choose erase all contents and settings. Once that's finished plug your phone back into iTunes and right click it from the menu. Choose restore from a backup and choose the most recent one.
Secondly, and I recommend this method, is to save your SHSH's. I think you will have to use ifaith if you haven't already done so. Check at the top of cydia to see what ones (if any) you have saved. Then you can follow my guide to restore your phone without updating it.
http://www.iphoneforums.net/forum/i...downgrade-preserve-firmware-your-iphone-9736/
f4780y's guide is great to help you understand SHSH's better...
http://www.iphoneforums.net/forum/i.../shsh-blobs-frequently-asked-questions-19986/
Sir/Ma'am, Thanks for the help. I have beeen using iPhone since Nov. 2012, so I'm really a newbie & don't understand
Several questions/
I clicked on your like about SHSH Blobs but didn't quite understand.
I seem to be stuck on iPhone 43 in 6.1.2
I don't quite know how I jailbroke, but don't quit know how to do it, because I see no advantage in it. I have several legitimate apps. I have tried the backup, reset all, then restore, but it's still jailbroken. Obviously I need some help?
Please be gentle, for I am a comparative iPhone newbie!