@Mike471 Call Airbnb and talk to them, they may give you a pass because you are new. For future, if you cancel a guest even at their request or N.B. at Airbnb's request, (sometimes Airbnb will send you a message saying do you want to cancel this guest - always say No, let the guest or Airbnb cancel it) it will result in myriad of penalties, fines, dates blocked, drop in search, host cancelled will appear on your reviews. Good luck.
p.s. There are a number of pitfalls for inexperienced Airbnb hosts this forum has a ton of advice, worth reading up on Instant Book, Cancellations, Smart Pricing, Cancelation Policies, Host Guarantee etc. to avert disaster. Here is a Tip Sheet from a Host which may be useful