can we run a worklet with out work flow?

No, You cannot run a worklet without a workflow.

A worklet is similar to a workflow with two differences:

First, a worklet does not have a Start task. So in order to execute anything within a mapplet, you need a workflow into which you can embed the worklet.

Second, worklet can be made reusable (if you want to group functionality into a worklet), but you don't have to; workflows are never reusable.