Your description of the problem sounds like it could indeed be an inflamed lymph node
. Although lymph nodes are not located on the collar bone, they are abundant in the neck region. The fact that it is painful to touch indicates that it is most likely due to an infection in the surrounding area. That being said, I want to make clear that this is in no way related to the sore throat
(infection) that you are also suffering from. The reason I believe this is due to the fact that an infection of the throat region would most likely drain to the lymph nodes below the jaw bone and in the upper regions of the neck.
It is possible that this node is inflamed due to to a symptomless condition much lower than expected, probably in the chest or abdomen.
If this condition still persists today, I urge you to approach a general surgeon
and ask him/her to take a look.
Hope this helps.