hello ,welcome to HCM.
From the history u have given it looks like is a viral infection or bacterial sore throat
swelling in neck could be coz of any local inflammation or trauma.
because of infection in throat it can lead to increase in size of neck lymph
nodes,it is a normal response of human body.
Having said that ,it can be a primary complex but less likely as it of recent onset and u noticed it yesterday only.
most likely report will negative and take full course of amoxylline and swelling will start reducing in size.if not then he has to undego full physical examination and CBC report to be done to know any infection going on.
hope i solved u queries.