avrdude -p atmega168 -P com60 -V -F -b57600 -c arduino -U flash:w:main.hexAs programmer just use arduino, not stk500v1 or v2 or tinyusb. change com60 and main.hex to your settings. Instead of atmega168 you might also use atmega328(p) which is more common on the nano nowadays. -V -F arguments are probably optional (no-verify, no signature check) :)