Your question isn't related to Pi-hole, but to your Virtualbox VM's network configuration:
It would seem that 10.0.2.15 is the internal IP address of your Virtualbox VM, which is only known within Virtualbox, while your home network is operating on the 192.168.1.0/24 range.
For Pi-hole within your VirtualBox VM to be reachable by your home network clients, you'd need to configure a route to your VM, or you'd need to configure your VM's network adapter connectivity to accept or forward traffic for the IP of the host running Virtualbox to your Pi-hole VM.
Either way, that would be a Virtualbox configuration issue.
See e.g. Pihole on Ubuntu Server in Virtualbox VM - #2 by Nakoma for a possible solution approach.