I had the same thing several times - thought, I would be cheating on my nose-plug in some way.
Luckily I repeated and did other things and didn't miss out on lucidity these instances.
What I do now is breathe out fully - irl and LD - and then do it.
Note how that feels irl - the snapping for air after you re-open.
That makes you believe it then in a dream! Did it twice since then in LD and it was fully convincing then.
Good luck!