The dynamics of fluid contained in a nano-cube has been studied by proposing theoretical model which is based on the microscopic consideration. The confinement affecting the movement at atomic level has been used to study the self-diffusion through Green Kubo relation. It is found that close to the walls, the dynamics of fluid slows down to an extent that it affects the flow of fluid even in the middle of the nanocube. Results are contrasted with the results obtained from similar considerations for fluid confined in rectangular nanotube. It is found that tendency of freezing near the wall is more in case of nanocube than in the rectangular nanotube. An empirical relation has also been proposed to explain the behaviour of wall mediated self-diffusion as a function of distance in either direction.