How to Make field required depending on other field? I have 2 fields in my content type "blog"

1)promote to front page(boolen field with yes or no option)

2)Hero Image(image field)

If user selects "yes" option in promote to front page field ,the Hero image field should become required.

How it can be possible?
You can do this with the Conditional Fields module.

It allows you to configure dependencies between fields (visible / required / etc.). It's still a development release, but it should work.