Plegridy

Hi. I’ve been using Plegridy since this summer and after taking the injection, the injection area never hurt before. But this time, when I was doing it to my back of the upper arm, it moved inside a little and hurt really bad. This was yesterday. I woke up today and it still hurts this morning. It’s not really extreme pain but it never happened before so I’m a little worried. Did anyone experienced something like this with injections? Thanks.