If you've accidentally clicked the 'on my way' button before it was time, you can reset the action with ease.
On the web portal, go to the job details page of the job that needs to be updated. Click the arrow icon above the 'on my way' button (OMW).
A window will appear for you to confirm. To reset the 'on my way' button, click 'undo OMW' in the bottom right.
'On my way' will now be cleared for you to click again at the correct time.