Swollen lymph nodes are a symptom of many things, not just HIV. It is a sign of an infection, so it would make sense to have a swollen lymph node if you were sick recently.

Mono is not uncommon in teens. Mono is kind of like a cold or flu that lasts a month and is often accompanied by swollen lymph nodes. It is contagious, but it usually no big deal and clears up on its own. If you go to the doctor for it, they will tell you that you have to go home and wait it out anyway. Here is a site if you want to read more about mono: http://familydoctor.org/077.xml

As with anything, we cannot diagnose you with any certainty over the internet. If you are concerned, then talk to your doctor or school nurse. If you are doing anything that puts you at a higher risk for HIV/AIDS, such as having unprotected sex or using needles, then get tested just in case.