HP-T5740/BCM57780/TPlink USB UE300 - Wireguard client

I have a thin client with a BCM57780 ethernet controller and a USB LTE stick E3372 HUAWEI.
Lan on BCM and WAN on LTE. OpenWrt is working after some configurations.

I installed wireguard packages and configured a wireguard client on the router OpenWrt.
This WG client is connected thru the WAN LTE to a WG server at home.
I can see that the IP address seen on a PC connected to the OpenWrt router is the IP address of the WG server. So OK on this side.

My question: how to access to a web server which is hosted on a PC connected on the LAN side of my OpenWrt router, from a PC connected on my home router LAN ?

for information:
LAN of my OpenWrt router: 192.1768.1.x
LAN of my home router: 192.168.0.x
IP address of WG seen on my home router:

Is there something to configure in the firewall section?

Thank you.

There are more than one ways to do it, however you'd better do it with s2s