"I'm an opened person" is wrong.
"I'm an open person" means "I'm direct. I don't hide my feelings. I don't act or put on a mask. You always see the 'real me.'"
"I'm an open-minded person" means "I'm willing to consider ideas that are new to me. I might change my mind."
"Open" is one of those words... according to one online dictionary it has twenty-two meanings as an adjective, ten as a transitive verb, eight as an intransitive verb, and five as a noun... forty-five in all, not counting phrasal verbs!
In this case, "open" is being used as an adjective.
I am sorry to say that "I am an opened person" sounds very strange indeed. It sounds as a surgeon is operating on you!