If you had a sore throat, that could definitely have been something to cause a swollen lymph node and they take a while to go down! Sometimes they don't even go all the way back down... I have one in front of my ear that has been there for years and years - over ten years at least now.
My children's pediatrician once explained lymph nodes to me in such a good way and I try to remind myself of it... he said that your body is constantly fighting off germs, infections, etc. Everyone's is. But fortunately, your body is set up for that. He said the lymph nodes job is to "catch" those infections and contain them... so that they don't spread to other parts of the body. And that's why they swell. In other words, he said, it is a sign that your body is doing its job and is NOT something to be concerned with. He said people probably have a lot more swollen lymph nodes all the time that we don't know about... but if the one that "catches" the invader happens to be in certain locations, we notice it more (neck, underarm especially)
The day he explained this, my son had a HUGE enlarged lymph node in his neck. Doctor wasn't worried. It took a few days to go down to a more reasonable size, and several weeks to go back to normal.