This is kind-of a tricky one, but totally doable.
If you add the ‘Recent Activity’ widget to your dashboard, you should hopefully see that some contacts have clicked this incorrect link. You will be able to click on the link in the recent activity widget, and this will open the Automation Link settings, where you can change the link name and destination. Once you save, anyone who clicks the link in the existing email will direct to the correct url.
Here is a quick example. I sent out an email broadcast and set a hyperlink to head to yahoo.com. In the video, I show finding this in my recent activity widget, and changing it. Check this out.