You pull it apart and see what you hit. Typically the motherboard is directly below the trackpad, so my guess is you did major damage to the circuitry. If you're using knives to try and fix laptops though, trying to disassemble it will probably just damage it more. Take it to a repair shop or someone knowledgeable with fixing laptops and ask them to take a look at it.
Just a dumb question, but by case knife you do mean the metal pocket knives and not some special "laptop case" knife, right? Sticking metal inside your laptop is a REALLY bad idea. Even if you didn't do physical damage you could have shorted out a component because the metal conducts electricity.