I have a medium size bump on the back of my head on the left side causing me to feel sick what is it? HELP?

Two nights ago I noticed a large bump on the left side of the back of my head about an inch higher than the bottom of my hair line. It didn't hurt unless I pressed on it really hard, I woke up yesterday morning and my entire left side of my neck was swollen and it's really sore. I got it checked by a doctor and he said that I probably pulled something in my neck causing a gland to swell in my head and it hurts because it is on top of a bone, he also said it could be a cyst. It wasn't until late last night i started feeling really sick and my whole back hurts. This morning i woke up with a fever and i feel like i have a cold. I don't know if this relates to the bump on my head but I don't think I pulled anything in my neck causing the gland to swell because the bump formed before my neck even started hurting. Please please please help! I'm going on vacation in 4 days so i really hope this is nothing. I'm really worried so pleeeeeaaaase help !