Isso foi respondido em um artigo do Sage Advice (você pode encontrá-lo no compêndio do Sage Advice).
Q: Can a bonus action be used as an action or vice versa? For example, can a bard use a bonus action to grant a Bardic Inspiration die and an action to cast healing word?
A: No. Actions and bonus actions aren't interchangeable. In the example, the bard could use Bardic Inspiration or healing word on a turn, but not both.