How do you remove a photo ( posted in error) from just one person and not have it completly removed from everyone such as a group photo attached to several people?
Then, definitely you should only need to delete the tag that links that image with that individual in Family Tree.
If I am understanding the question, you would just need to remove the incorrect person tag. The image won't be deleted. Keep in mind you can only remove tags that you added.
Here is an article that goes into more depth:
I posted a photo in error to the wrong person. I want to remove that photo from the memory on that person with out removing it completely from the Family Search archive.
Look in Help Center for "How do I edit or delete person tags in Memories?"
In Family Tree, if a photo or document shows up on the wrong person, it means that memory contains a tag to that person. Any user can fix this problem by detaching the tag, which removes it from the wrong person’s record.