"I saw your lesson request, but when I saw *it* it was late"

If I want to say:

I saw your lesson request, but when I saw it it was late.

Is it correct to use the first it? I know that in this sentence the first it function as a pronoun, and the second as an idiom. If this sentence looks awkward, please give me a suggestion to improve it.

It is correct; however, I would place a comma between it and it or (better) just replace "when I saw it" to say:

"I saw your lesson request, but by then it was late."

Yea, you need to add a comma between it and it.

OR (better). You could use

By the time I saw your lesson request, it was late.

-EDIT- Looks like someone beat me to it. His answer is just as good, if not better. But I can't upvote it, since I'm new here.