In the article says that Nicaragua will send for consideration the volcanic lagoons that lay in its Pacific rim side, on the basis of their biodiversity. Of course, this is not yet on the TList, so probably the article refers to the inclusion of that list.
There are two of these volcanoes mentioned: the lagoon of the Cosigüina volcano caldera (which produced a cataclysmic eruption in 1835) and the Apoyo lagoon (a popular tourist spot). It is not mentioned the near Masaya volcano and its lava lagoon (already on TList since 1995) which most probably, wouldn't apply on the basis of biodiversity, but on geological interest.
I find it great that our neighbor, which has only 2 WHS, intends to nominate additional sites in the future. I find it however very curious that all of the sites that have been proposed/ mentioned recently are on the Pacific side of this country.
In the Caribbean side of the country there are a couple of TList sites (Bosawás and Miskitos Keys), but there could be a higher potential to nominate other natural sites. Indeed, IUCN's Filling the Gaps report, in its conclusions, mentions the "Mosquito Coast forest along the Nicaraguan Coast" as a priority for Central and South America. This would be represented by a potential nomination of the huge conservation complex on its southern border (that includes Indio Maíz Biological Reserve and Punta Gorda Natural Reserve, and could also include the Tortuguero National Park and Barra del Colorado Biological Refuge, across the border in Costa Rica). As there are indications that the crazy idea of the Nicaragua Canal has become stagnant, there is maybe potential for conservation. http://www.panorama.com.ve/mundo/Nicaragua-postula-lagunas-volcanicas-como-patrimonio -de-la-humanidad-20171009-0106.html