Botulinum toxin treatment is quick and isn't painful; you'll just feel a 'sharp scratch' of the needle when it is injected.
There may be some redness and swelling, which will calm down a few hours after treatment.
You'll start noticing a difference in the appearance of your chin after a couple of days, with a complete result noticeable following two weeks. The effect will last three to six months before you'll need a top-up to maintain results.