Lump on the side of my toddlers neck?!

Lump on the side of my toddlers neck?

I am really hoping to can be reassured by some other mums out there becasue i am becoming increasingly worried about my 20 month old son. My mother in law noticed a small lump on his neck about two weeks ago. I took him to the Dr and the Dr has said it more than likely is just a swollen lymp node but he has given me a referral for my son to get a blood count... what would this be for? Is this t check for cancer?
He also diagnosed my son with glue ear and thinks the lymp node may be enlarged due to fighting infection. I am extremely worried because the lump is quite large. about the size of a 20c peice. It doesnt seem to bother him when i touch it and he isn't in pain. It has been there for almost 3 weeks now and hasn't gone down at all. he is on antibiotics for the glue ear and has been on them for almost a week.
I am so worried that it may be cancerous. Ifanyone has had a similar expericne can you please tell me!
Thanks.

My son is 3 years old now and has had a small lump on his neck since he was born. For the longest time everyone thought it was a lymph node, as it would sometimes get bigger. But, just three days ago we saw a different pediatrician who felt it and said it was just a fatty cyst. He explained that cancerous lumps feel more "lumpy" and don't move - they're stuck to the tissue. But, his cyst is very mobile and small and round. He said most people have them around the hairline of the neck and behind/below the ears. He also said it's absolutely nothing to worry about and doesn't need to be removed. We thought it was a lymph node for so long because it's in that area, and it seemed to get bigger when he was sick. What a pleasant and simple explanation - and a big relief. As your pediatrician if it could possibly be a fatty cyst.