Cross Country question! I'm freaking out!?

My first time running cross country, even though i've ran track for two years. I'm worried. I can't even run a mile. I've been running since the middle of July for three times on a track. I can run three laps around a track without stopping. I'm freaking out. I told everyone I would tryout and I have this feeling if I don't tryout people will think I'm a liar. I'm just really worried. 3 miles would kill me. Ughhh. I'm worried I would be at a met and I would have to walk it. See, in track I'm a sprinter. I just need tips.