In braces treatment tramatic ulcers are common. If it is because of any projections on the wire or brackets(button like metalic part on the tooth) you can use ortho wax on the sharp areas. It will help you from trauma by sharp edges.
Next Steps
Try to adjust with ortho wax. This you will get from your dentist itself or you will get from online sites. And if it is unbearable and you need to quit. There is one more option, that is clear aligner. Which is transparent and you can search in YouTube videos. This doesn't hurt. But cost in little more
Health Tips
While doing ortho treatment try to maintain a good oral hygiene, because most of the surface is covered with wire so food will stuck . So brush twice daily. And in proper way.