Do you feel under the weather at all? Do you have a cold or flu? 9 times out of 10 swollen lymph nodes are a result from infection, so most likely it's nothing to be concerned about. Normal lymph node size is about 1 cm (pea sized), so perhaps your node wasn't really enlarged previously?
Keep an eye on it and if it doesn't go away after a few weeks or if it gets bigger, you should probably have it looked at by your doctor.
I forgot to add that I am a 19 year old female, in otherwise healthy condition