Thanks for the question.I recommend that you discuss your concern with your doctor
. Any part of the body that doesn't heal after trauma is something that should be watched closely. In this specific part of the body, there are several possible explanations. The first is local trauma that caused scar tissue that is taking quite a long time to heal. Massage can help some scar to reorganize and soften over time, and that should be something that you can do yourself. Beyond the normal scarring, there are hyper-active changes to the skin that can occur such as keloids. Certain ethnic groups can be more likely to have these, and your previous history of healing can provide clues as to whether or not you are likely to develop keloids or other over-active healing processes of the skin. Next, there are many small salivary glands on the inside of your lip that can be traumatized. Some of this trauma can result in mucous backing up within the gland, a mucocele, or other enlargement of the gland. Finally, there are nerve injuries that can result in local swelling, although these are less common. Again, speaking with your doctor will be helpful, and an ear nose and throat surgeon
may be a good start.