I got my first COVID-19 vaccination shot (The Moderna one) the Saturday before last (Jan 17th). It went well. No side effects at all the first day. Some pain and swelling at the point of the injection (upper arm) for the next two days, which I was told to expect. Then the pain and swelling went away and I thought "That wasn't so bad."
Last night (Jan 25th), 8 days after the injection, the spot where I was injected starting itching intensely, felt hot and was swelling up. The swelling was actually worse than the swelling a week ago. It kind of freaked me out.
Did some checking online and it turns out this is a pretty common. They're called reactogenicity symptoms (side effects that happen within 7 days of getting vaccinated). Apparently a lot of people are reporting this.
Just wish I had known ahead of time that it might happen. I figured I'd post my experience so others can see it.
I got my Influenza (right arm) and Pneumonia shots last November, about a week later my left arm was in pain. As of today I still have mild pain in my shoulder, my doctor told me is just my age but I read online the Pneumonia shot has this side affect. I hope your problem goes away faster than 3 months.