Oh hon, I read this and had to write immediately. We had the same exact thing happen. My son was about 3 years old and one day when we picked him up from daycare, he had a huge lump on his throat. To make a long story short, our family doctor sent us to the Ear Nose and Throat doc immediately. The doctor checked our son over and coldly said, he either has an infection or cancer (called it some big name I can't remember). She said that we need to treat it with an antiboitic and in 2 weeks if the lump doesn't go away, then it is cancer. I was dumbfounded!! How could they just send us home and wait 2 weeks to see what happens? Thank the Lord, the lump was gone within almost 2 days and life is great. Come to find out a couple days later, there was another little girl in the day care that had the exact same thing so it was contagious.
By all means, get your son checked but also ask the daycare if any other kids had the lump.
You are in my prayers, L. Faber