I will assume that you went back to your doctor when you finished the antibiotics for another UA to make sure the infection was gone?
I guess the lymphnodes on the right side of your neck were not bothering you then or you would have told your doctor.
Do you have any other symptoms? It IS the cold and flu season and quite often the first sign your body is fighting off an infection is a swollen lymph gland or two. It's possible that the infection in your bladder/kidney was not totally eradicated by the first round of antibiotics. Perhaps it has returned and is presenting itself as swollen nodes in your neck. Call your doctors office and speak with his nurse. See if they want you to come in for another UA. It is not unusual for some infections to require a second round of antibiotics.
If your mind is pretty much set on cancer, I guess all the reasons I could tell you why it ISN'T cancer won't matter.
If you're scared, see your doctor and then ask for a referral to a therapist to begin working on your anxiety & hypochondria. Both of those disorders can be fixed and I promise you, your life will be a whole bunch better without them. Trust me, I lost a good many YEARS dying from one thing or another. I'll NEVER get those years back. What a stupid, stupid waste!
To help the tenderness of your swollen gland, STOP POKING AT IT. The only thing that will help it go down, (if it's even "up") is TIME.
Call your doctor.
Peace
Greenlydia