I am a 19 year old female last week i felt a lump in my jaw line inside mouth. really worried. what could this be?

If it persists...: Go see your family doctor and get an examination. Your dentist might also be able to check it . Lumps in the mouth can be from any number of causes, from swelling of your salivary gland(submandibular gland) to tooth infection and if it does not go away in 2-3 weeks we want to make sure it is not growing which can raise a question of cancer although it is not high on my list of possibilities.