You mean for example my home network is running NordVPN via router and my mobile devices are also on NordVPN but away from my local network work as a local network?
Well now you've introduced a *second* OpenVPN server into the mix. The one from NordVPN, and your own for home access. What you would normally do in a situation like that is route ALL the traffic from your mobile devices through your home OpenVPN server, which provides LAN access, but if the destination was for the internet, that traffic would be further routed through the OpenVPN client (connected to NordVPN) on the router.
But that's a completely separate issue from what you initially asked. Anytime you need to run the OpenVPN client and OpenVPN server of the router at the same time, you need to use routing policy (i.e., the VPN Director). And in the case described above, you would include the OpenVPN server's IP network on the tunnel (e.g., 10.8.0.0/24) in the VPN Director.
Admittedly, some of this is going to sound confusing until you just make the attempt to get things working.