Filing for citizenship soon,. Arrested and not arraigned. Case was dimissed. NEED HELP

I was arrested yesterday at my place of work. At first I didnt know what happened. Detectives came, cuffed me and I was given the explanation that the store had counterfit bags. There about 15 pieces in the store, and I never though it woud ever be a problem. I told them I was not the owner. They didnt care. The owner came in 10 min and told them to let me go. He took the responsibility, but they said; NO PROBLEM. WE ARE JUST GOING TO GIVE HER A TICKET AND LET HER GO.
It turned to to be all a lie. They keept in the Precint for hours. I was begging them to let me go, but no, they didnt not.
I was fingerprinted and taken a photo. Then transported to Central booking. I was in a cell for about 9 hours. They were saying that I would be releassed but not when. Finally after 9 hours I was called by an officer. Handed me a piece of paper and told me that all charges agaist me were dismissed. I didnt need to see a judge or nothing.
The paper said that the record of this arrest was sealed and that I was not arraigned either.

My question is:

I am applying for my citizenship in about 20 days. Is this going to affect my case?
How should I answer the questions about the criminal record ?
I think I shoud say that I was arrested but not convicted>???????
should I insert any coppies of the letter they gave me?

I am really scared. PLEASE HELP>