how did the hole get made? What version of C4D (are the points that were at the corners of the polys still there)? If the points are still there use them and the poly pen to recreate them. Otherwise maybe use that inner layer and Split a matching set of polys off that and Scale it out if the inside is as close a match as it looks… *edit* why the inner layer I ask myself, it just looks obvious through the hole… Because it looks like a lathe you should be able to select a matching set of polys somewhere around the object (on the outer layer) and rotate them into place. *edit*
Or maybe a set of Circle splines matched to the edges with the same number of points as the lathe has circular subdivisions and use that as the base for the poly pen…