Under right jaw I have lump. When I look to the right downward, and turn head upright I feel lightheaded, dizzy. Lymph under arm and neck tender, causes?

Lump a concern. I suspect the lump and the dizziness are unrelated. The combined movements of your head which you describe might make anybody dizzy by slightly compromising the blood flow in your neck. This is not particularly concerning. However, lumps need attention and if it persists for a week or so, along with the tenderness, see your doctor for evaluation, especially if it seems to be enlarging. Good wishes.