Nigrán sits due west of the camino, to get there turn left on the first road after the camino path narrows near the roundabout mentioned above.
Entering Vigo: Please read carefully to understand the many options, pitfalls, tips, and why it is the way that it is.
The official camino into, through, and out of Vigo does not really exist. Due in part to party politics, and in part to uninhibited urban sprawl, the way has been erased and rewritten on many occasions. Marking the way are yellow arrows, green arrows (if you find your way to the O Freixo albergue), stone markers, and most recently several hundred blue and yellow stickers put in place by well-intentioned shop owners. With regard to these stickers, be aware that they don't really follow any path; they are all over town and their only helpful characteristic is that they mostly point North. And with regard to the stone and arrows, they are on occasion in disagreement and the path you follow might come down to what side of the road you were walking into town on… and therefore which of the two caught your eye first.
Before you go any further, do yourself a favor and open the map to familiarize yourself with the solid line that goes through Vigo, and the two alternate lines (in Red) which go around it. One of those paths goes around town to the west and the waterfront. The other goes to the east and although it does enter Vigo it avoids all of the nicer parts. Take a note of where they split.
SPLIT 1: You will have been walking along the road for some distance when you get to a roundabout. Here is where you have to choose. To your left, in front of a small home, is the stone indicating the way through/around Vigo along the coast. Fifty meters beyond the roundabout are arrows pointing to the right, that is the way around Vigo to the east as well as the way to the O Freixo albergue.
The best advice I can give is to turn left as the two options from here are the only ones which take you through the heart of Vigo. Then pay close attention to where the path splits again.
SPLIT 2: The camino splits a second time when it gets to the Rio Lagares: to your right, the arrows take you through Vigo. To the left, there are no arrows but it is a short walk to the sea and from there you simply turn right and keep the water to your left. Both of these routes rejoin at the start of a new pedestrian path that has opened in the old port, and not far beyond that is the new Xunta albergue (completely unmarked, you'll need to refer to the map again). The path through Vigo is not the official path (remember that no such thing really exists) but rather follows the easiest route down to the port where the albergue is, as well as the Basílica de Santa María de Vigo and some of its more charming barrios. Vigo is full of these barrios, they are an anomaly in a city that is the poster child for unplanned expansion. They are like small villages shoehorned into the cityscape.
From the river split, the route along the coast is the most scenic of the three options and will only cost you 1 additional kilometer of walking for the benefit of fresh are and much quieter walking. This option also passes through Bouzas (restaurants), one of the oldest and largest of the villages that make up modern Vigo.