Hi thanks for your question.
Lymh nodes are normally present in body and get enlarge in two conditions.
1.If there is infection in the vicinity of lymph
2.in Lymhoma that is cancer of lymph node.
Most common cause is infection in their vicinity.Since your supera clavicular lymph node are enlaged most probably you have infection some where in your sinuses
,throat and even ear.
The best way to get you out from tension is go for FNAC (fine needle aspiration cytology) of enlarged lymh nodes to know the cause of enlargement of lymh nodes.
Hope this answers your question.