I've asked this same question...and yes, it could cause damage. Apparently there is a diaphram and causing restriction could cause damage to it so you should probably untie the knot.
My test kit for nitrates doesn't register in the amounts like yours. But, if you are doing regular water changes, missing a week shouldn't hurt.
Mustcooktea asked a great question, what amount are you changing? I usually change around 25% a week with the occasional stretching to every 2 weeks. I only have test kits for nitrites, pH, and ammonia and *knocks on wood* are usually ok.
What size is your tank?