What is on your mind/ in your mind?

Which one of the above bold one is correct?

Does the above mean one and the same. What the person has in his/her mind. what the person is thinking about?
Yes, that is what they both mean. 'On' is the usual collocation, but it usually means more specifically 'what is worrying you?'
SynonymWhat is on your mind?
As stated above, "What's worrying you?" "What have you been thinking about?" "What is it that you have been hesitating to say?"

That's not the same as What do you have in mind? ~ "What suggestion(s) do you wish to make?" "What were you thinking of suggesting?"

What is in your mind? is not a standard expression. I wouldn't use it if I were you.