Having braces or aligners fitted is not a painful procedure. However, for the first few days afterwards you may feel some discomfort, ranging from mild irritation and tightness to pain when pressure is put on the teeth. In some cases there may be jaw pain or a headache. Braces can also cause sore spots on the inside of the cheeks and lips, which can add to the discomfort. Despite this, you can carry on going to school or work as normal.
This answer is for general information. Your own case needs an examination by an orthodontist.