Hello, I have gone through your query and understand your concern. it is most probably a Mucus retention cysts. It is usually caused by sucking the lip membranes between the teeth. As it is very small and nothing to be concerned about this too much. It may rupture spontaneously and heals on it own. It is not advisable to prick and open the cyst, as it may get infected. Better leave it alone. You should consult a dentist or surgeon, if it is bothersome by its redness, pain. It may a sign of infection, then he need antibiotics and painkillers. Hope this helps. Please write back for further queries. Wishing you good health.