The pin-prick flash is the Pi trying to read the SD card. The Pi does this once or twice a second to see if an SD card is still inserted. It uses this method as the SD card present pin is not connected on the Pi. I presume this is used to detect if the SD card has been changed.
Okay - the problem was a silly one.
I just unzipped the raspbian lite img file and copy pasted the disk image.
I decided to reformat the sd, and use etcher to write the entire img file to the sd, and BOOM! It works!
I am sorry I have made too many stupid wild guesses in this answer. My explanation of the faint green led blinking is plain wrong, and suggestion to fix is ridiculously silly. Please ignore what I have said below. My apologies.
Rpi3A+ act led starts green solid, then blinks once,
then pinprick green steadily ...