Adding one competency for the content section

Content

We have a requirement to identify one competency out of the all added competency list as the primary one for the employee. Since current system design does not support for it we have raised an ER for it.

As an alternative we decided to create a content section using competency template and ask users to maintain primary skill there. Since this section also similar to the existing competency section users can add more than one competency in that section. We need to know is there a way we can allow user to add only one competency in the content section?