What do you mean "stop reading data through Bluetooth"???? What/who is actually the receiving entity? Embedded FW on nRF5x chip or some mobile app? BLE data are typically coming as asynchronous calls through some lower-stack API (typically from GATT Client/Server layer) so if you don't want to bother with them then just happily ignore the events, if you don't like to receive things over BLE at all then simply disconnect. Otherwise solve issue on sender's side (it should probably stop sending data if receiver cannot process them fast enough).
