Okey dokey, so I did as you suggested, reburned the bootloader to the nano via the uno, that went without issue. I then disconnected them (nothing connected to any pins on the nano), plugged the nano into USB, changed the settings to board: nano/328p, port: COM5, programmer: AVRISP mkII and clicked upload, and I get this error:
Arduino: 1.8.5 (Windows 7), Board: "Arduino Nano, ATmega328P"
Sketch uses 928 bytes (3%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude -CC:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM5 -b57600 -D -Uflash:w:C:\Users\HALO2F~1\AppData\Local\Temp\arduino_build_756897/Blink.ino.hex:i
avrdude: Version 6.3, compiled on Jan 17 2017 at 12:00:53
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"
Using Port : COM5
Using Programmer : arduino
Overriding Baud Rate : 57600
AVR Part : ATmega328P
Chip Erase delay : 9000 us
PAGEL : PD7
BS2 : PC2
RESET disposition : dedicated
RETRY pulse : SCK
serial program mode : yes
parallel program mode : yes
Timeout : 200
StabDelay : 100
CmdexeDelay : 25
SyncLoops : 32
ByteDelay : 0
PollIndex : 3
PollValue : 0x53
Memory Detail :
Block Poll Page Polled
Memory Type Mode Delay Size Indx Paged Size Size #Pages MinW MaxW ReadBack
----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
eeprom 65 20 4 0 no 1024 4 0 3600 3600 0xff 0xff
flash 65 6 128 0 yes 32768 128 256 4500 4500 0xff 0xff
lfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
hfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
efuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
lock 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
calibration 0 0 0 0 no 1 0 0 0 0 0x00 0x00
signature 0 0 0 0 no 3 0 0 0 0 0x00 0x00
Programmer Type : Arduino
Description : Arduino
Hardware Version: 2
Firmware Version: 1.16
Vtarget : 0.0 V
Varef : 0.0 V
Oscillator : Off
SCK period : 0.1 us
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: reading input file "C:\Users\HALO2F~1\AppData\Local\Temp\arduino_build_756897/Blink.ino.hex"
avrdude: writing flash (928 bytes):
Writing | ################################################## | 100% 0.30s
avrdude: 928 bytes of flash written
avrdude: verifying flash memory against C:\Users\HALO2F~1\AppData\Local\Temp\arduino_build_756897/Blink.ino.hex:
avrdude: load data flash data from input file C:\Users\HALO2F~1\AppData\Local\Temp\arduino_build_756897/Blink.ino.hex:
avrdude: input file C:\Users\HALO2F~1\AppData\Local\Temp\arduino_build_756897/Blink.ino.hex contains 928 bytes
avrdude: reading on-chip flash data:
Reading | ################################################## | 100% 0.22s
avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0288
0x0e != 0x06
avrdude: verification error; content mismatch
avrdude done. Thank you.
the selected serial port
does not exist or your board is not connected
That has to mean that I toasted the ch340, right? Just for completeness, I unplugged that nano and plugged in a brand new one, and uploaded the blink sketch without issue, on the same USB port too.