Question

Where can I sell my Big Nugget in Black/White?

Answer 1

You can sell items at any pokemart.

Comments

That's what I though too.

Answer 2

Don't sell your Nuggets or Star dust at Pokemarts. If you hold onto them until you get to the 7gym town. You can Sell it to an old man in the Pokecentre for Double what the pokemart buys it for. Unless you're tight for cash I'd hold out for him.

Answer 3

The Big Nugget cannot be sold at Poke Marts. Instead, a man in Iccirus City's Pokemon Center will purchase it for $30,000.

Big Nugget (Bulbapedia)

Answer 4

You can't sell it at the poke mart
Try anvil town