Type /speed in chat if you're running the premium version or use one of the portals that only lead back to your point of origin if you're not. You can then walk or sprint out by holding left shift, but this will take a long time depending on how far away it is. If you don't want to wait, type /resettle in chat and try again. For a faster way to travel between points in a large world, consider using something like Archero.