Of course Norseman were the first Europeans to discover and colonise the Americas. However, the later rediscovery of the Americas in the late 15th century has had a much larger impact on global history than these early expeditions.

While Inuits weren't in Greenland yet (as they didn't exist as a culture at the time), there were definitely humans living in Greenland when the Vikings arrived. The Norse and natives (called Skrælings by the Norse) developed a relationship of sorts - sometimes they traded, sometimes they fought. They mostly fought.

Part of the reason why the Norsemen were unable to expand in North America, and at least a contributing factor of why they abandoned their colonies in Greenland, is because there were natives there. It was difficult to expand into Vinland and other parts of modern day Canada when the natives didn't want you there and were prepared and equipped to fight you off. Similarly in Greenland, the locals (named Skrælings by the Norse) were always in conflict with the Norse. Iceland didn't have a native population (maybe just some Irish monks), so exiled Norsemen could relatively easily settle there. It was difficult to be profitable and stable in places like Greenland when you're trying to get walrus ivory and farm all the while trying to fight off angry, well prepared, well adapted locals.

Edit: And maybe someone started taking the Norse legends a lot more seriously after Columbus's discovery - it's certainly possible. Or maybe someone asked an Icelander and they said "oh sure that place from the saga, it's just over there, can't miss it"