The position of the lips and cheeks, which shapes how our face looks, depends on the position of the teeth directly behind them. For example, if the upper teeth tilt forward a lot, this will make the lips protrude. Sometimes the lips even close with difficulty, or the patient keeps their mouth open. If these teeth are moved back as part of orthodontic treatment, the lips will follow them. The same is true of the opposite situation – teeth that sit too far back lead to lips that sit back, and correcting the teeth changes the appearance of the lips. An underbite (reverse bite) of the front teeth shows in the face as a prominent chin and lower lip and a retruding upper lip, because with this problem the upper teeth sit behind the lower ones. Correcting the bite will change the lips too.
This answer is for general information. Your own case needs an examination by an orthodontist.