could be a cyst. But this is something you should get checked out by a doctor, in person, to see if it's not something more serious. He might want to do a biopsy, or remove some or all of the excess tissue inside your neck to find out what it is and rule out anything serious. Even if it's not bothersome, it's always good to rule things out.
Hi there. There are many possibilities of swelling neck one side. It could be enlarged lymph node or thyroid lobe, submandibular gland, lipoma, sebaceous cyst etc. a surgeon needs to examine it to further come to a diagnosis. Some times fine needle aspiration cytology may be required for diagnosis. Take care.
Are you talking about the front left side or left side under the ear or back left side?