Welcome to Healthcare Magic
It's possible it could be a lymph node infection
. But this is not the only cause. Since if it has appeared recently it is quite possible. You need to get him shown to a Paediatrician to rule out infection in the body part which is causing his lymph node to swell up because Lymph node is like police, it usually alerts to the site of infection. Kindly look for any other such swellings and/or symptoms and signs like chest pain
, abdominal pain
etc. to help your Paediatrician diagnose and treat him. GOOD LUCK !!!!