Mistake on Naturalization form?!!

Hi All, looking for some help as I suddenly feel I've made a huge mistake on my application form for naturalization.

On my form, I ticked no previous immigration application, how looking back, I feel I should have ticked yes, since I applied for indefinite leave to remain in 2006.

I submitted my application on Feb 28 and have since submitted my biometrics.. Should I contactthe home office with a written explanation for this mistake or is it too late?

This is giving me a lot of sleepless nights now as I feel it may lead to a refusal

Any advice would be greatly appreciated. Thank you.

That is perfectly fine answer. Do not worry. They are not asking you to tell them about your immigration history or ILR. You already entered you held ILR