Could this be serious? Like cancer?

I'm physically healthy but mentally drained, stressed and depressed 21 year old. I noticed last night that I have a little smaller-than-pea-sized bump behind my left testicle. I was reading what it could be and one possibility was AIDs. That's a possibility because they say healthy people who develop a rare cancer is a sign symptom of AIDs. I don't know if I have testicular cancer; I'm waiting for the doctor's office to open at 9. Does this make any sense? Could this be the case. I'm going to see a doctor but I want to have an idea of what's up right now..