Maryland possession laws?

So i was recently in ocean city, md for vacation and our townhouse got searched because when the police officer came in to make us dump out alcohol and what not(we were underage) he found a tiny little bit of weed on the counter. He searched the rest of the house but did not find anything else. My name was the only name on the lease so i was the only one who got arrested and charged out of the 5 other people staying with me. I don't smoke weed, haven't in 4 years. I even offered to take a drug test to prove that it's obviously not mine but he didn't give me one. I got charged with possession and paraphernalia because it was in cellophane.. I was just wondering if they have a case? can i really get charged with possession when it wasn't found on me or in my luggage or anything? Should i plead guilty or not guilty?