What have i done?

[mustickman]

Hi guys long time reader first time poster.

I own a 2006 Fiesta and i left the lights on the other day so i went to jump start it from my other car and i accidentally put the leads on the wrong way..
What damage may have i done? i cannot start the car now even with a fully charged battery, the immobilizer light flicks fast when i turn the ignition off, so im thinking that it is stopping me from starting the car. any help would be greatly appreciated.
Regards Shayne.