Posting in different categories

in the “widgets” section, I can add categories, in the post section, I can also add categories. The problem is the categories that I create in the “post” area will appear under the categories declared under all the widgets. Example: in the “widgets” I add the categories “one” and “two”, now after I finish writing a post, I can also add/pick a category to put the post ie “uncategorized”, this category appears under both “widget” categories “one” and “two”. Is there a way that I can pick just one “widget” category section to put the post in instead of it appearing in all the “widget” categories?