What happens if you get a summons for unlawful possession of marijuana?

Last night I and my other 3 friends was smoking weed in the car and the cops pulled up right in front of us. Basically they searched the car and everything and gave only me and the driver a summons because the blunt was found in the cup holder next to us. I have a clean record and have no idea how this process could or will go. I am 19 and my financial aid was just processed 3 days ago and it went through successfully so does that mean I will get aid for this coming year? Or will they take it back? Also I cannot get an attorney because I can't tell my mom anything. If it gets dismissed will it stay on my record? If I have to pay a fine will it stay on my record? Will this show up on my record and affect my application for jobs and grad school? Lastly, the cop said "if you pay the $25 within a week you'll be fine" what the hell does that mean? If that's the case why'd he give me a summons? I'm so confused and I'm really scared because nothing like this has ever happened to me before.