Rats will chew through anything you try to plug the hole with. The most humane way to take care of it is live trap it and move it. You can also buy a rat trap from your local grocery store.
I have found that D-Con works the best but you need to make sure that if you have cats or dogs or small children in the area that you are putting it then you need to make absolutely possitive that you are putting it where they cannot get access to it in anyway it has lye in it.
You'll need to get rid of it. Use a rat trap. Bait it, set it, and get it out the next morning. If you are squeemish about killing and disposing it, you can use a humane trap and have animal control take it for you.
If you want to kill the rat get a sticky trap. To capture the rat and let it go free someplace else, get a trap cage and put peanut butter on something that can't me moved and this will give the trap enough time to trigger the cage door.
