Misspelling of the word 'niggy' which is a different version of the word "nigga". The 'P' is silent so it's still pronounced 'niggy', unless you are talking to someone in real life and you wanted them to notice you were using the word 'pniggy'. But 'pniggy' is just meant for IM and chat. How this word was mispelled? Nobody knows, because 'P' is so far away from 'N' on the keyboard. It makes no sense, yet it happened.
Person 1: What's up dude?
Person 2: nm but that pniggy Eddie owes me money!
Person 1: pniggy?
Person 2: *niggy, but whatever.