I think you're sadly barking up the wrong tree and also suggest the Outer Borough board, though I haven't really seen much talk about Nicaraguan food there either.
I have popped into Casa Fox on the LES on a rainy Saturday for drinks and empanadas. The owner is Nicaraguan, and they have Tona, as well as some small plates. Not terribly cheap or rustic, but it was enjoyable, and the space is cool. They often have a fire lit. http://www.acasafox.com/restaurant.html
If you do manage to find a good Indio Viejo around do let us know.
A couple of years ago I bought a bag of Salvadorean dulce de nance at Centroamerican Deli and Grocery, 2601-A Bergenline Ave., Union City, New Jersey; 201-867-7447.
The shopkeeper, who sold food and gifts from all over the region, was Nicaraguan, according to my notes, and he might be able to offer a lead. If you do find prepared food from Nicaragua, please report your findings here! Good luck.