Did i kill my plant?

No, it's not dead. Depends how bad is the cut and how the plant has managed its "inside system". It could recover, besides, the right side looks still "connected" (from the picture). I would try to cover the wound to prevent any infections and definitively wait a good week before saying it's dead.

Just wrap it with anything ya got. It should heal back up and you can remove it in a few weeks.

What smoke24 said. Just wrap it up in something like plastic wrap, tightly, and tape it up. You want to keep the area humid (which is why you wrap it) to help it heal. I used garden ties to tighten mine back up when that happened to me.