Arduino NANO: only PWR LED lit (faintly) – dead?


I've been playing around with an Arduino NANO clone over the weekend. Everything was perfectly fine at first (board alive and well, passing basic tests). This evening I've programmed an ATtiny85 to do a blink test (with an external LED), and then a button test (both powered using only the USB connection). The latter did work out as well as the first one (obviously) but then, while making a video to show it off (:D), I've pressed the external button a few times in a row, and it all stopped working. I took the duino NANO out of the breadboard to check for signs of life and all I can see is the red PWR LED lighting up faintly, blinking if I press the reset button. Arduino IDE does not see the board connected to any of the USB ports anymore.

As I am an absolute newbie, simply looking for a new hobby, I am lost. Found some tutorials on how to attempt to repair Arduino NANOs that have similar issues, but I am not even sure how to diagnose mine, don't know what is the problem exactly. What to do? Any help would be appreciated.