I have noticed a hard peas size knot at the back of right ear of my 13 month old son, immovable & appears to be non tender since my son was not bothered when I touched it. He does not have fever, runny nose, cough, not pulling his ears. What could be the cause of this?
This is most likely a lymph gland. It can occur with, as you rightly think, ear, throat and nose problems, but also due to infections and injuries of the skin of the scalp and the surrounding areas. If painless, you need not do anything. It will either remain the same, or gradually reduce over years.