If you pay the fine after you get your full licence you should be fine. I was in a similar situation, and i waited until after I got my blacks to pay the fine and I still have my licence. That was over 6 months ago. The RTA even sent me a letter saying I was running out of points (or had too many, however you want to put it) but that was based on the 12 you can have on a full licence. The offence that put me over the limit for points on green p's was for a missing p plate as well, so it's not as if they wouldn't have noticed that it happened before I got my full licence.