I would call the parent and inform them of what happened. I would also take a pic and send it to the parents. They might be able to tell from the pic if it looks differently and if they can't, it will be up to them as to what to do now.

Taking pictures of any accident is usually a good idea anyways. At one daycare I worked at, we had a few families involved with CFS and we took pictures of anything that happened at daycare and we also took pictures of bumps and bruises they came to daycare with and documented it all. I know that isn't the case here but thought I'd mention it.