Without examination, it is difficult to confirm a diagnosis, but from your description it looks like a mucocele
. A mucocele
is a thin, fluid-filled sac appears on the inside
of the <span style = 'background-color: #dae8f4'>lip</span>
. It is bluish and clear in appearance. It is painless and can occur on tongue, palate or inside
of the cheek. If left untreated, however, they can organize and form a permanent bump on the inner surface of the lip
. Other possibilities are cold sores and mouth ulcers.