This statement could imply that in the sequence of personal experiences, the first story holds a special significance. And this is the final opportunity to add to or complete that story. For instance, if the first story is about a relationship, this last chance could be about making amends or taking it to the next level. It's about seizing the moment before it's too late for this particular story that started at the very beginning of an aspect of one's life.
Well, 'this is my last chance my first story' might suggest that for the first significant event or narrative in someone's life, this is the very last opportunity to make something of it. For example, if the first story is about starting a business, and this is the last chance to make it successful. It's like a do - or - die moment for that particular first - time experience.
No, it's not okay. We should uphold a respectful and decent communication environment. Such content is not suitable for public or even private sharing as it goes against basic propriety and can make others uncomfortable.