If your bracket or band is still attached to the wire, you should leave it in place and put wax on it if needed for comfort. If the bracket or band can be removed easily, place it in an envelope and save it to bring to your next appointment.
Using a pair of tweezers or needle-nosed pliers, try to put your wire back into place. It is okay to use a piece of floss to tie the wire into place: tie the floss around the bracket in place of the missing colored o-ring. If you cannot put the wire into a comfortable position, and covering the end with wax doesn't help, as a last resort use a small fingernail clipper to clip the wire behind the last tooth to which it is securely fastened. If the end of the wire is still sharp place wax on it.
Using a pencil eraser, push the poking wire down or place wax on it so that it is no longer poking.