Hi
Could u please attach a photograph.
It might be oral mucocele,any trauma / injury to Minor Salivary glands present on the lip.These are usually painless.
Reasons could be:
Trauma
Lip biting habit.
Damage or blocked ducts
Nothing to worry about it,it ll heal by itself.
Keep observing if there is any change in size and shape,it can be surgically removed .
Hope your question was answered
Next Steps
Consult a nearby dental surgeon if u find changes over a period of time.
Health Tips
*Avoid lip biting or sucking habits
*Maintain ur oral hygiene