Okay, help, I'm really really really scared!!!?

Okay, Im just gonna tell it all how it happened exactly. I am 13 years old btw, and a girl. I was walking to school this morning (on my own) and there was a man I sometimes see walking down the path. He has two greyhounds and I umed he was just an innocent man walking his dogs. He kind of slowed down to a stop, so I walked ahead, not talking to him, and as i got further along I thought I heard him speed up. Then I felt something on my leg, what I umed was his dog and that's what he told me as I turned around to see what it was. He then said "Can I have a favour?" And I knew I shouldn't talk to him, so I said "...Urm, what?" and he said "Can I see your knickers?" So I said "No!" and ran off as fast as I could for what usually takes me ten minutes to walk. I then just started walking normally as I would be to school, but I was absolutely petrified. I was really all day and still am. Especially about walking to school tomorrow. I'll probably go a different way, and go at a different time, but still, I'm SO scared. Please help, what should I do? I dont really want to tell anyone...