In this work, we consider the diffraction of TM waves by an open metal-dielectric waveguide, a Goubau line (GL), with a nonlinear inhomogeneous dielectric cover. Numerical experiments are carried out for the nonlinearity with saturation. The physical problem is reduced to solving a nonlinear boundary value problem for a system of ordinary differential equations. Numerical results are obtained using a modification of the shooting method which makes it possible to determine and plot the amplitude of the reflected field with respect to the amplitude of the incident field. Comparison between the nonlinear problem and the corresponding linear setting is performed.