I,m looking for a solution to trigger an action on Openhab with the use of an external NFC reader - (Just like the function on the Android App).
Anyone have any suggestion I’ll be happy 
external to what server & os? OpenHAB is cross platform.
With an External reader I mean one that’s NOT attached to af phone running Openhab client (Android).
I want to send the UID of a particular NFC tag to Openhab and process that UID to trigger Action/Rules.
I assumed you meant external to your OpenHAB server. see why we needed more detail?
LIkely if you are connecting an NFC Reader to ypur phone it would depend on the OS version & tne manufacturer’s customizations 
I would like to achieve this without a phone - a NFC desktop reader USB or RS232, and transmit the UID to openhab - I don’t need the payload of the nfc chip.
Have you looked to see if it can be done with an esp8266 with some sort of reader?
Decided to go with a Rs232 reader, connecting that to a TCP/IP - Serial gateway and using the Serial binding.
Hopefully this will work