Let it dry out for a while before you do anything. Maybe drain the air box in case water got in it. Also if there isn't a washer / gasket on the spark plug put one there and / or tighten it a little bit more. Or could it be just water boiling off? If it is it is nothing to worry about.
As for gunk inside the cylinder I don't know. There will be carbon build. Is that what you wiped up?
My 2 cents worth.