That is not a file Pi-hole would use by default.
Pi-hole's embedded pihole-FTL (its own tailored version of dnsmasq ) would use /etc/pihole/dhcp.leases , if you enabled its DHCP server.
The existence of that other file in that location would often indicate a separate dnsmasq instance running.
In your case however, since you seem to be using a Beaglebone, you likely suffer from a SoftAP configuration that is reactivated on system reboot unless you specifically disable that behaviour (see Failed to resolve via localhost (127.0.0.1) - #10 by amespuga)