The tooth of my implant came off and the screw is still there. What should I do?

Sorry you are having a problem. It sounds like your crown came uncemented from your implant post. You should see your dentist as soon as possible to recement it. It might be too late but you should place the crown back onto the post to keep the gum tissue from falling over the implant. You can use a very small amount of tempgrip (Denture adhesive that can be purchased at any drug store). Place this into your crown and it will hold the crown until you can see your dentist. It is not the end of the world if your gums do fall over the implant but it does simplify recementation of your crown. All the best to you.

Sorry to hear about your problem . You need to call your dentist and have them reattached the abutment and crown to the I Implant .  Very easy to do