Why won't my computer boot up?

I just fixed my heatsink today, and after putting everything back together my computer would power on but the keyboard and mouse wouldn't work. I looked under the hood again but now my computer won't start up at all. The only thing I've noticed is that the cable for the keyboard/trackpad seems to have split along the side -- as in, the plastic casing has split open but the wires are intact.

Help! I just spent a bunch of money to get a new battery and to fix the heatsink, and I really don't want all my work today to have gone to waste. (I'm also in a foreign country with few resources so finding a new keyboard might be tough.)