It does sound like you damaged something, depending on what you damaged you may need a new HD, HD cable assy or worse the logic bd if you hit it with the knife.
Do you see any damage in any of the areas you were working in? Also check the connectors haven't been damaged and/or not mated together correctly.
If that doesn't point the way:
I would first start with an external HD (firewire) which has mac OS-X on it (bootable) to see if the system is working. If you are able to get it to come up thats a good sign the issue is either the HD it's self or the HD cable assy.
If you can get an external drive enclosure (FW or USB) you could try installing the HD in it and see if you can gain access to it. That then leaves the issue of a bad cable in which case you'll need to get a replacement.
NOTE: you can't disconnect the boot drive so if the external HD you booted from doesn't have a second FW port you will ned to use a USB connected enclosure to connect the suspect HD into (unless you have access to a second Mac system).