Just clean, can probably take a small pick or paper clip and stick through it...if you were looking down the plug hole at the same time you'll see it stick through to your plug.
If your plugs are out make sure nothing is pushed in where it can fall into your cylinder...
As a matter of fact, you can do a drain test by spraying a little WD-40 down you plug hole (with the plug in) and it should drain out through this little hole and come out near your header tube. Might even be behind your header flange if you have stock headers.