I have horner 's syndrome right arm pain i have had no treatment i am very afraid should i be worried?

Horner's syndrome: Needs explanation. It can be caused by a lung cancer which has also involved the nerves to your arm (if the affected eye is on the same side as your arm pain). Please see a neurologist very soon.

Concerned: The fact that you presented with horner's syndrome with right arm pain means it probably is a second-order neuron lesion. This type of horner's syndrome can be from something minor like a cervical rib to something serious like a pancoast tumor, tooth abscess, or neuroblastoma. How were you diagnosed? Ct chest done? Chest x-ray? How long have you had it? Need more data.