I have completed every Nick Rye quest. I went to the Seed Ranch before visiting Nick at his airfield and triggered the start of his first mission there and got him as a companion. I continued with the missions involving his wife. The icon did not go away. Now I am approaching every mission complete in the region and have researched this bug. It's been unresolved for over two years now it seems. People reported the exact same problem I am having this very moment. Now, this may not be a game impeding glitch, although it might be as some reported being unable to 100% the game because of it. But a glitch none the less and I would think a simple one to actually fix. I've tried to look for modding for assistance before even thinking of posting here as it's likely going to be completely overlooked. No dice. So with a fart of a prayer, here I am.
Hey, iKorv1n!
Sorry to hear that you are still experiencing this issue, we are aware that the map marker could remain and unfortunately, this issue does not have a timeframe for when or if it will be resolved.
I understand that this is not the news you were hoping for and for this we apologize. If you need further support please let us know.