If you have a full screen information dialog (or even a full screen dialog with more than information e.g. settings), you could place a "Back" button at the button instead of an "OK" button, since "OK" is more common for smaller pop-ups.
("OK" makes me think, "OK" I have read this, close this window. However, if the windows is full screen, I can't tell if it will close the previous window too. "Back" does not cause such an ambivalence.)
Specifically, on Android phones, there is always a global back button (or at least in all those I have seen), so omitting the "Back" button within the dialog would fit in with the OS's UX.
(If you do rely on the OS back button, make sure that users won't go back twice by mistake due to a long press or an additional press due to slowness in responding to the first press.)
If the information dialog does not completely hide the previous dialog (is not full screen), then an "OK" button would fit in with common UX. Clicking outside the dialog could be a useful secondary means for closing the dialog, however, you would have to leave a margin around the dialog that doesn't close it in order to prevent the sausage fingers effect from cause accidental closure of the dialog.