Big game for both sides. Nigeria need a win to stay alive, Iceland can put themselves on the brink of qualification with a win.
There's one other side who have a keep rooting interesting here - Argentina. If Iceland wins, than Argentina will need to 1) win 2) hope Iceland and 3) catch Iceland on goal differential in order to qualify. If Iceland draw or lose, things open up a bit for Argentina.
I ran the numbers, and Argentina are roughly 50/50 to advance if Iceland doesn't win today, and Argentina are ~15% to advance if Iceland do win.