Help for a boot loop

Hello people,
I was playing with an old phone and suddenly i rooted it [not by mistake]. First the phone worked fine and i tested few root apps, but one week later when i shutdown the mobile i couldn’t turn on again. Searching on Google i found is a thing called boot loop, i can see the brand of the mobile [Wich is an Xperia Lumia] bit after this it automatically reboot. I remember root it with rootking, but i tried other tools, so i don’t know exactly wich one do the fail.
I will apreciate any help because now i’m having issues with my mobile and i want to use the Xperia.
Thank you.