Thank you for writing to us.
I think that you have a lesion on the arm which is infected. It is possible that you have an insect bite or some other cause. You can also have a pimple which is causing the swollen skin infection.
Also, you may have a cyst which is causing the problem. See a Doctor to diagnose it and reach the cause. Post this, treatment will be surgical or it will be by medication to help you recover.
Hope this helps you.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.