First Time Rider

Im 14 and I just barely bought a dirt bike for my birthday, I got home and rode it a bit on some dirt roads, Im done riding and come home and right on the street leading to my house, I got pulled over, I'ts only about a quarter mile to my house from the dirt roads i was on, The officer tells me what im doing is illegal and should go home, I still have no idea what I did wrong, could someone help?