ThatchedNugz

I'm just curious of what kind of punishment could I be facing? Here's the story:

Last night my cousin and I were leaving a party, following another friend in separate vehicle to a different party. My cousin was driving, I was shotgun and no one else was in the car. We get pulled over because my cousin's car headlight was out, and for changing lane w/o signaling. The cop suspects alcohol and performs a field sobriety test on my cousin, which he passed, but he refused a breathalizer so the cop arrested him. He then asked for my id and to step out of the car and wait by another cop that had showed up. The arresting officer then searched my cousin's car and found his pipe and one-hitter and my one-hitter.
The cop asked me if anything in the car was mine, and I answered him honestly that one of the one-hitters was mine. He then cuffed me and put me in the sqaud car with my cousin. Neither of us were read our rights btw. We were processed at the local jail and I posted our bails.
This is my first offense and my record is otherwise clean, what sort of punishment can I expect? I live in Illinois.