An open mind is a noun:"You should keep an open mind about this". You can´t use it to describe "person". Here you should say open-minded , two words with a hyphen.

What is correct open mind or open minded?

If you have an "open mind", you are an "open-minded" person. If you have a "closed mind", you are a "closed-minded" person.

Is open mind one word?

having or showing a mind receptive to new ideas or arguments. unprejudiced; unbigoted; impartial.