If you didn't get any items, you'll have to wait until the next week when a new boss spawns. World bosses do a lot of damage and it's helpful to have a healer or two keeping you alive.
Though grouping isn't mandatory, it's beneficial to use the party finder to team up with other players-especially if you can't find other players already nearby.
Fortunately, when you get to the spawn point of a world boss you'll typically find dozens of other players looking to kill it too. That quest's icon on the map will be surrounded by the gold spikes used to denote elite enemies.
