I have a swollen lymph node behind my ear on the mastoid bone but no sign of infection and has been there for over a month what could it be?

Lymph nodes that are: Small, not growing and stable in any part of the body are mostly benign. Lymph nodes are responsible for filtering any infection, inflammation around the area involved or it's a sign of tumor itself. Always follow up with your dr for any concerns. Take care!

Your friend: Nobody knows why certain people have more lymphoid tissue in different areas. A node like this that is freely movable and not growing is there to help you. Leave it alone and be thankful for good health.