Warbler said:

well about month ago a robin made a nest in the bend of the gutter right in front of the kitchen window of my house. We watched it make the nest, sit on the eggs, and feed its babies once the eggs hatched. Once the babies got big enough, they all left the nest. My mom, who knows a little bit about birds, told me that once a bird is done with a nest, that it is for the nest. Birds do not reuse an old nest. So, after being told to do so by my mother, I knocked the nest down.

A day latter, which was last Saturday, another Robin starts building a nest in the exact same spot! It has finished the nest and is now sitting on its eggs.

The general consensus is that US robins don't re-use old nests but European robins (which are an entirely different species) do.

So you are in the clear Warb.

You didn't upset your feathered friend's hard work, in fact you helped him/her out by clearing what is clearly an advantageous spot of a dirty old nest so he/she can build a new one.

They will continue to lay until around July/August.