No worries - we've all added people that we needed to change later. So the easiest thing to do would be to re-use that profile for another relative. If you don't have another relative in mind at the moment, then you would just need to remove all the links to it.
So for the first, just go into the profile and edit all the information to make it into the other relative (change the name, birth date/place, biography, etc.). Then change the parents to the new parents for the new person. And remove any spouses or children that might not be needed.
Or just remove parents, spouses, and children and set it aside so that you can use it at a later time.
I know all this might sound confusing, but WikiTree does not have a delete feature so merging or deleting is the only way to handle eliminating a duplicate.