minor error on cv / app. form


Hi guys.

To my annoyance I have made a minor error on my online application form (which has already been submitted btw)

For my finals at school, I achieved a B3 in French, but what I put down on my appliction form and CV was B2.

If I inform the employer and tell them it was a mistake, I cant help but feel they will view it as sloppy and bin my application straight out.

If I say nothing, and should it get to the stage where I’m offered the job, I may be background checked and they’ll notice the result on my school grades is different to what I gave n my app. form and CV.
Its not as if I’m going for a job that needs French, but they may view this as lying as deceitful, as opposed to a mistake.

What should I do? Contact them? Ignore it?

Suggestions greatly appreciated!!!