What should I do if I find a mistake in my submitted master's thesis? What would you do if you have already handed in a thesis to your professor, but you printed an earlier version with a small mistake. You want to have a great grade nevertheless, but I am feeling unsure of what to do: 

Would you tell him your mistake and hope that he indulgent and says "Okay, then this does not count as a mistake." Since you recognized your own mistake, he is likely to be forgiving. Or would you say nothing and hope that he won't find the mistake?
Everyone makes small mistakes from time to time and it is expected that there should be some mistakes in a master's thesis. What you should perhaps do depends on the nature of the mistake. If you are talking about a small or even a big typo, I would suggest just leaving it be and not alerting your professor. Typos are expected and a few won't impact your grade very much, if at all. However, if you have made a major scientific, analytic, or other substantive mistake, acknowledging it and offering a correction is the right thing to do. Depending on the rules of your institution, the professor may not be able to accept a modification to the document you turned in, but if they can, you are sorted. If they can't, them knowing that YOU know that this was a mistake is likely better than them finding the mistake and thinking that you don't know, from a grade point of view.