My throat hurts when I swallow. But only on one side. And it's not really my throat but right under my throat. Is this something I can treat at home or do I have to go to the doctor?

There's no way anyone online can know.
Your title says 'swollen gland,' yet you don't mention feeling one, just that your throat is sore sort of under it. Not good detail!
People don't have to rush to an ER to sit there for hours with people who are coughing all over each other.
So... try a few things:
1) Look at your throat with a flashlight or lamp bulb with no shade, and go AAHH.
2) Feel around your neck and chin and throat and tell us what you feel, if anything, and where, and how big.
3) Gargle every 30 minutes with warm water with about a teaspoon of salt in it, and gargle way back without swallowing.
4) Brush your teeth and your tongue.
5) Keep warm, and put a silk scarf around your neck, or any scarf.
Answer back.