If it was a genuine mistake I can't see it being a problem. Just do the extra hours at the end. But watch yourself cos if you knew what you were doing God will probably throw it back in your face when you get to heaven so best to just come clean now if you're trying to pull a fast one(sorry).
Nothing, where and when in the bible did Jesus say we had Lent ? As far as i can remember didn't he command us to go out and make disciples of all nations.
He never once mentioned Lent, so where did you get this idea from; a priest or some church dogma. Don't worry about it, I'm sure your salvation does not depend on you breaking lent, rather it depends on accepting Jesus, as he asked you to do.