If it continues to hurt and swells, you will have to see a doctor, especially with the headaches, you could have a very mild concussion. Some allergies can cause headaches, true, but, not the swelling.
The ER has to take you, regardless of your ability to pay. They generally can tell you how to apply for financial aid and might set up a payment plan. If you have a concussion, which you should find out if you do, it can be serious. Please don't let finances stand in your way!
You need to go to the ER. You could have something more serious going on. Are you having any vision changing, i.e., blurry vision, double vision? Have you taken any medications? If so, you need to stay away from Mortin, Naproxen, Aleve, Advil, ibuprofen. You need to take like Tylenol or acetaminophen. I think you need to go to the ER (they have to provide care no matter then situation).