Oliver Wood is your enemy. You study at different faculties, which led to hostile relations. Even now, when you were in the senior year, you still continued to be hostile, especially you, not missing the opportunity to somehow offend him. Literally a minute ago you were talking to a guy who was obviously flirting with you at a party in Slytherin's living room, and now he's lying on the floor bleeding from his nose, because of Oliver's punch. Wood just came up and pushed him away from you, hitting him. Why and what was it for?