Error: can't get into admin controls

I recently bough a theme to be used with my WP and i’m a novice with this. I installed the theme and after installing the theme i realized that it had some text that was standard and nothing i could via customizing the theme would change it. I went into the theme data and tried to modify the HTML coding instead, which didn’t change it.
My problem:
I can’t log back into my admin or dashboard page to change it back because it gives me the error message: “In order for Contrast to function properly, please don’t modify the theme data.” I can’t get passed this screen to where i can change the data back to what it was. The page mikealder.com works (not how i want it to but you can at least see it) but i can’t log into the admin:mikealder.com/wp-admin
HELP!