I've heard this one on multiple occasions:
Sometimes you need to toot your own horn.
However, that wording is usually meant to say that you need to promote your own strengths, but not necessarily show your weaknesses.
Although some dictionaries define toot your own horn as a way of boasting, I've heard it used in contexts where someone is not boasting, but perhaps should be letting someone know a little more about the behind-the-scenes work they have been doing; for example:
Ed: You worked hard on that project! I'm surprised you didn't get the promotion.
Ted: Maybe so, but I don't think the boss knows much about what goes on around here after 5 o'clock.
Ed: Well, Ted, sometimes you need to toot your own horn.
If you want to emphasize that you are sharing both stengths and weaknesses, you could say:
I'm going to lay my cards on the table.
which is used as a metaphor to describe being totally candid about an issue.
I don't think either of these match the Persian proverb completely, but they both have a bit of overlap.