cleansing of an old immunization?

Hi,
I am on day 24 of Humaworm. A few days ago, I noticed my deltoid muscle in my left arm was really sore. I did not remember hitting it or anything happening that would make it sore like that. The next day, it was still sore and I looked at my arm and it had a red spot. This is strange, but the soreness almost felt like the soreness after getting a tetanus shot. I am wondering if it was the cleansing of a past immunization? The red spot was right in the area where the injection would have taken place. My imagination???