You can’t access Mikrotik router if it’s behind NAT (which is owned by ISP).
But you can open the tunnel from your Mikrotik to VPN server, especially if you have another Mikrotik router with public IP. And I mean this: http://forum.mikrotik.com/t/mikrotik-behind-nat-to-mikrotik-ipsec-ike2-with-certs-tunnel-eoip/144952/1