I'm writing a narrative essay and I can't figure out the most correct one between "I was chose" and "I was chosen".
I was chosen is correct. The passive voice always takes the past participle form of the verb, not the simple past. So, I chose, I was chosen.
With most verbs (all the regular ones, and many of the irregular ones), the past participle and the simple past form are the same, so you don't have to concern yourself with the distinction: Joe finished the book, the book was finished by Joe. However, Joe took the book, the book was taken by Joe.
Here's a list of irregular verbs. Again, to form the passive, use a form of the verb to be with the past participle.