What can cause pentagon-shaped inflammation at the covid vaccination site? ?

So my friend and I got the pfizer vaccine two days before this photo was taken. She had really bad soreness and pain at the site of injection, and showed it to me. It's in the shape of a pentagon????? I know inflammation at the site is very common, but the affected region should be radially distributed right? I cant think of any reason the distribution of the mRNA would go like this. 

I would like to preface this next part by saying that we're not radical christians or anti-vax in any way at all (she's not even christian lol) but like there is a small star shape of whiter skin inside the pentagon! 

Again, I'm not saying that this is something mystical or a reason to not get vaccinated. I just want to know if there is any biological explanation for why a fluid or an inflammation response would mount in the shape of pentagon around an "infection" site and start to clear in the shape of a star???? Calling all biology experts!! I'm super curious!