Dear Madam The swelling at the side of the neck or lump aredue to(1) Infection In any infection in the region of neck head throat ear may give rise to swelling of the neck glans which try to fight infection.(2)Cystic swellings that includes (a) Brachial cyst (b) Cystic Hygroma
.(a) Brachial cyst is congenital anomaly and got cystic swelling with liquid inside.It is usually painless but if it gets infected it may be painful.(b)This is also a congenital anomally with swelling due to multiple cysts
inside. Both needs removal by surgical intervention. (3) Neopastic like Sarcoma
. These are painless swellings. My advise is you should see an ENT Specialist
to have through examinations and investigations and treatment. Kindest regards.