Assuming the coordinates on your JourneyMap display are accurate, unfortunately the biome seems to be generated on a corner where four regions intersect, so you will need to delete four regions.
Assuming that this is the Overworld, find your saves directory, open the save, find the folder named 'region', open it, and delete the following regions:
- r.-4.-1.mca
- r.-4.0.mca
- r.-3.-1.mca
- r.-3.0.mca
Note that I would make a backup (copy) of your save before doing this just in case something goes wrong (e.g. if something important turns out to be in the affected area, or if the save can no longer be played). I would also recommend that your player not be in that area (e.g. by exiting the game while in your base rather than over the affected area).
This will wipe out a 1024x1024 block area around the affected area. This essentially means anything that you build, gravestones, mobs and animals, terrain, etc. are erased. When you return to these areas, the terrain and animals will be regenerated. Most generation should be the same as it was originally since it is generated from your world seed. Only worldgen that does not use the world seed will change - this will probably just be certain random features from a few mods. And, of course, the area that generated improperly due to the biome ID conflict will generate as it was supposed to with the proper biome (assuming that you corrected the conflict - if you didn't change BoP's config or disable Thaumic Horizons, the broken biome will just generate again).
If you don't want to delete such a large area, open up MCEdit and just delete the affected chunks.
Once you've modified your save and deleted the affected areas, open it up again in Minecraft. Check to make sure that the area has indeed been regenerated properly, along with checking that all of your creations are intact.