Human nature usually leads us to jump to conclusions. We get really nervous when we find a new lump, bump, or mole on our body, because we know it doesn’t belong, and it wasn’t there before. We tend to get even more anxious when it is a bump or lump on our child. Well, if your child develops a soft swelling in the mouth, it could simply be a mucocele, which is a harmless cyst.

A mucocele is found on a small salivary gland and often swells into a cyst when one of the saliva ducts in your mouth is damaged or blocked. Everything from biting your cheek, to sucking on your lower lip can cause damage to the ducts that makes a cyst form.

A mucocele can usually be found on the inside of your lower lips, your gums, or the roof of your mouth. They are moveable, painless, soft, round, dome-shapes, and are usually clear or bluish in color. While mucoceles are harmless and usually go away on their own, if it does stick around and become enlarged, go see your dentist. Dealing with it on your own is not a good idea, only your dentist or doctor will know the right way to treat a mucocele.

http://www.webmd.com/oral-health/guide/mucocele-causes-symptoms-and-treatment