My son is 25 years old. He has had a lump on the back of his neck for about 10 years. The doctor told him that it was a pimple/acne that grew inside instead of outside and to keep an eye on it. It has been the same size until today. It has gotten larger & it feels like a pinching sensation. Two days ago, he went to a Walgreen's clinic because he had an ear infection. The doctor who treated him said that it was a good thing that he came in and that it was very red inside and quite a large infection (he was having yellow discharge from his ear) and she put him on 875mgs of Amoxilcilin. To me, it sounds like the Amoxicilin is affecting the lump. Do you have any ideas? Thank you.