Dear Anonymous. A swollen gland is always an indication that something is not "right", especially so if it is painful as well. I take it for granted that there is no wound or something similar on the arm that could be the cause - otherwise you would have mentioned it.
Any abnormality like this should be examined so that a correct diagnosis can be made for early treatment.
I would like to suggest that you make an appointment with your family physician for this to be sorted out. (MCH).
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.