I have my mikrotik router plugged into my main router. The mikrotik has an IP address of 192.168.0.30 from my main router and also it’s 192.168.88.1
I can access the webfig panel when connect to the WiFi on the mikrotik but when I am connected to the WiFi on my main router I cannot access the webfig panel using 192.168.0.30 is there anyway to change this?
I suppose your “main router” already has a firewall protecting you from internet attacks. If it’s true, you can delete all your firewall rules in RouterOS (menu: IP → Firewall) and try if your network works as expected. If not, reset your router to default/factory settings and start again
I don’t have enough information about your network to answer that, but RouterOS doesn’t listen to port 1723 by default (you can see the ports and services in IP → Services) so I GUESS your MikroTik device is safe.