In this paper we discuss the MHD unsteady flow of a micropolar nanofluid through a vertical channel with expanding/contracting walls under the influence of nonlinear thermal radiation considering weak permeability. The PDEs of the governing problem are reduced into a set of ODEs by using self-similar transformations and are then solved numerically. Influence of flow parameters such as wall dilation ratio, permeability Reynolds number, micropolar parameters, thermal radiation parameter, nanofluid parameters etc. on the flow, thermal energy and volume fraction of nanoparticles has been discussed in detail. We trust that the results of this study are not only useful for industrial applications but also present a basic understanding of the physical model.