Go up and speak to him, if he ignores you still, walk off and just have fun with your mates and he will come around by the end of the night

Either out it in the airing cupboard for one week or liuke said above, put it in a bag and fill it with rice because rice is super at absorbing water and will get into the cracks, try the airing cupboard first and then the rice if that hasnt worked. Good Luck!! Xx