You can only have one bonus action per round (and only one action, and only one reaction).
And to add to this and clear up possible confusion (or possibly create some), you can't use your bonus action as a regular action. Bonus actions are bonus actions, and actions are actions, and ne'er the two shall meet.
Example: a monk/cleric (or Rogue/Cleric - class doesn't matter as long as it allows Dodge as a bonus action for this example) uses a Ki point to Dodge (as a bonus action). He then uses his movement to move toward his comrade (unconscious), to get within range to cast his Healing Word spell. Note, he still has his action, and wants to use it to cast Healing Word (bonus action) instead - but he can't do it.
The relevant rule can be found in the PHB, pg 189 under Your Turn:
On your turn you can move a distance up to your speed and take one action
followed by the subsection immediately below, under Bonus Actions:
You can take a bonus action only when a special ability, spell or other feature of the game states that you can do something as a bonus action.
and in the following paragraph...
You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available.
And, since I mentioned it above the relevant note for a Reaction is on page 190 of the PHB under the Reactions section.
When you take a reaction, you can't take another one until the start of your next turn.
Finally, my note about not being able to use a bonus action as an action (more applicable to spellcasting than anything else) is referenced in an unofficial tweet by rules designer Jeremy Crawford in August 2014, and reiterated (with the same example) in an official ruling in the Sage Advice Compendium:
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?
No. Actions and bonus actions aren’t interchangeable. In the example, the bard could use Bardic Inspiration or healing word on a turn, not both.