That would limit your options. I have not fished around Nelson much so my knowledge is mostly second hand.
These a couple of fishing platforms next to the main road which follows the coast. Never fished them myself but often see people there. Also the entrances into the estuaries over the raising tide, the entrance into the Rabbit Island inlet (waimea Inlet) can be productive.
If you can get out to Pipin Island, walk/climb along to the 2nd point (or further). Maybe a 20 minute walk, been told the 1st little beach/point is rubbish and it is worth the effort to go further.