There is no way out of a bad situation except through.
Go back, train hard, say nothing to him, except an apology for your actions. No doubt he was wrong, but you are not responsible for his actions, only yours.
Walk through this and you'll be much the better for it. Learn. There is no shame in making a mistake, once you've taken responsibility and made proper amends. There is great shame in acting like you are right when you're not.
And when all is said and done, in a hundred years, no one will remember, keep perspective.