Fog-assisted 5G Networks allow the users within the networks to execute their tasks and processes through cooperation among the fog nodes. As a result, the delay in task execution reduces in contrast to the task execution in independent scenarios, where the Base Station (BS) is directly involved. In the practical scenario, the ability to cooperate clearly depends on the willingness of fog nodes to cooperate. Hence the prime purpose of this study and project is to design an incentive-based bargaining approach based on Nash Bargaining Solution (NBS) which encourages a cooperative task execution by the fog nodes for the end-users in a fog-assisted 5G network. The proposed model encourages the fog nodes to cooperate among themselves by receiving incentives from the end-users benefitting from the cooperation. Considering the heterogeneous nature of fog nodes based on their storage capacity, energy efficiency, etc., we aim to emphasize a fair incentive mechanism that fairly distributes the incentives from users to the participating fog nodes and improves the QoS. The proposed incentive-based cooperative approach reduces the cost of end-users as well as balances the energy consumption of fog nodes. The proposed system model addresses and models the above approaches and mathematically formulate cost models for both fog nodes and the end-users in a fog-assisted 5G network.