lincoln Lee seemed to know Nick (from our universe), how do Du think they know each other?

I don't remember their interaction very well, but I don't think they knew each other

Difficult, I guess that there also was a Nick on their side

when they all crossed over to the other side to rescue peter...when nick was on the bridge dying, agent lee sagte "nick?", not sure how he knows him, but i'm guessing he obviously knows the one on the other side (meaning his side)