Yesterday I created a portal, teleported into the Nether for the first time since the update, tried to leave the Nether and was unable to teleport. On reloading, Minecraft took me back in time to when I hadn't started building the portal. 

Today I rebuilt the portal, teleported to the Nether, walk forwards and noticed there is no portal behind me. I am now stuck in The Nether.

What to do...?