etiquette - Professor wrote me a letter of recommendation, but sent it to both me and the institute

So after all these crazy days of trying to finish my application and encouraging professors to finish the letters of recommendations (LORs) for me, there is the next thing - my professor sent the letter of recommendation (which he had to send just to the institution) also to me. I think he did it unknowingly, but now I am stressed again, because I should not know the content of the letter of course. I didn't open it, but this situation is quite crazy. If I can see that he sent it to two recipients, it stands to reason that the another recipient can see it too.

Uhh. Does someone know what should I do now?

EDIT: It was a letter related to the grant application