Found an error in my thesis I've found a error in my thesis recently, after its submission. I made a mistake that wrongly accepted the hypothesis which should be rejected. What should I do??
It is normal that a thesis contains mistakes and wrong conclusions. If you did not yet do your defense, it is not a problem. The examiners may find and mentione it. Otherwise, you do it by yourself the day of your presentation, by indicating that honest mistake. You can then correct it in the final version of your thesis. 

If your thesis is already in the library and you got evaluated for it, try to talk to your adviser and he will suggest either to ignore it or to add a correction on the website or as an extra document in the library.