Umm.. Move away, if you can get to another dimension, way better
Then go to mcedit, select chunks and delete them
Then, mark them for remake
next time you get into the overworld it will regenerate everything
(Thats what i usually do when i install mods or something that add world gen but don't want to make a new world, it works almost everytime.. (i found some problem with thaumcraft for example, it seems that it will not "regenerate" its structures unless you told it to do so
in the config you can find the proper option)