Give it 2 or 3 weeks. It won't just pop up one morning. It will be a gradual thing that you might not even notice at first. Next thing you know, you'll be looking at ugly girls that you never looked at before and saying "Unnnngggghhh, bend over doggie." Or you'll start whacking off after you see your sister's underwear in the laundry basket. Or you'll start sporting wood when you watch your grandma working in the garden. Or when you see your grandpa's false teeth in his cup, you'll start dreaming of a gum job. Strange shit like that.