Baby giving herself arm hickeys.

My daughter will be 2 months old a week's from now answer she is EBF. She has a new found obsession with her hands and arms. Well last night I left her with someone for about 20 minutes while I ran to grab some food to bring home. I came home and she had left a hickey on her forearm where they let her suck on it. I'm furious. I have a doctor appointment next Monday for her vaccinations but I don't want them to think I abuse my baby. Has anyone else had this problem!?