Spawn somewhere else in the nether?

I play the MC pocket edition on my cell phone, and now I have a world in which I have built sooo much, now I want to build a few things in the nether as well. I built a portal, decorated it very elaborately, went in and was quite disappointed: an endless lava lake and no fortress far and wide. Now I wanted to ask if I can "reset" the portal so that I spawn in a completely different place. Is that possible, or do I have to build a new portal somewhere else?

(I don't know if this is important, but I bought minecraft as normal via google play store, not via Tutu app or anything else)

As far as I know, the portal can't simply be "restarted" but must be built from scratch.