Hi, I have the same concern as below. I had a flu shot for the first time on Monday. On the Monday night I had really bad aching under and around my armpit at the injection site. Then on Wednesday I noticed a small lump that was painful on my collarbone toward the neck area on the same side as the injection. I went to the doctor and he thinks it could be a reaction but hasn t come across it on the collarbone before and has suggested an ultrasound. Is this common? I feel healthy otherwise.