I left my health card in my room and I need to go to the hospital

Unfortunately, residences are closed off to students during the holidays, so you can't just go in. You could try calling Security (dial 88) and see if they can help you if it's an emergency.

Without your healthcard, you can still go to the hospital but you'll receive a bill in the mail. You can always explain the situation to the hospital and let them know that you will call in with your health card information when you retrieve it (on the 5th or 6th) and they will then bill OHIP once they have that info. Most receptionists are very understanding when it comes to that stuff and you should be fine.

Your healthcard will not cover any ambulance rides and you will be billed $50, I believe, if you need one to take you to the hospital.

Best of luck and I hope you get better soon.