Pissed! I don't know what to do!

Courtney
I currently have custody of my nephew. About a year ago my brother in law was arrested for child abuse charges and domestic violence charges (all charges were dropped last month). My sister was so shaken up by the incident and mentally unstable that I was awarded temporary custody. 
Anyway, the other day my nephew's father had visitation so I took Jayden and dropped him off. When I picked him up he was sleeping and had a hat on so I didn't see this until I got him home. His hat was stuck to his head and when I finally was able to ease the hat off blood gushed everywhere. I rushed him to the ER. He needed 5 stitches. The cops couldn't do anything because it was an "accident". They did say that I had the right to keep him from his father since there is no parenting plan in place yet. But I don't know if that would be the best thing? Would keeping him from his father just be hurting Jayden?