Should I be worried.

Mo • Mama ×3 ❤

I went to check on my daughter's last night after bedtime. I went over to cover my six year old when I noticed this on her arm. I asked her about it this morning and she said she doesn't know where it came from. I know what it is and I googled it to see the causes (which I know I shouldn't have) and some scary things came up. Should I be worried?