I found a lump in her neck

On Monday a found a lump in my 3year old neck. It seems to be a swollen lymph node. She had her vaccination today, so I waited until today to ask if I should be concerned.

The nurse said to come back if it hasn't disappeared in 2 weeks.

I was stupid enough to Google and I'm now so confused. She has no other symptoms and hasn't been ill in months. The last time she had a common cold was in June.

She said first it doesn't hurt. Today it seemed a bit harder than in Monday and when I asked her she said it hurt when I touch it, but she didn't seem in pain when I was actually touching it.

I know this is really silly, but I'm so scared of the worst case scenario. Especially because just two days ago we found out that my niece has a brain tumor. Now I'm even more nervous.

Anyone elses child had a swollen lymph node with no other symptoms and it was completely fine?