I have a small movable lump on my jawline that's been there for years. it doesn't hurt and hasn't grown or changed. what could it be?

Lymph node: That is probably a small lymph node. We have them all over our bodies, and there are especially a lot around the head and neck. It helped you clear out an infection years ago, and just stayed a little larger. Also, there is a salivary gland that wraps under the jaw on each side, and you may be feeling the duct from that gland. No worries.