A scraped knee on the playground is a completely normal, healthy part of growing up. However, to a highly anxious first-time parent, a minor scratch can look like a massive failure of center supervision. The absolute best trick to managing minor injuries is the preemptive morning phone call.
Do not let a parent find out about a facial scratch when they walk in to pick up their child at 5:30 PM. The surprise factor is what triggers their anger. Call them at 10:30 AM right after the incident happens. Say, "He is totally fine, and he went right back to playing in the sandbox, but I wanted you to know he tripped on the mulch and got a small scrape." Tell them you already washed it and applied a bandage. It defuses the entire situation before they ever see the injury. Proactive transparency is the single most powerful tool in your parent communication arsenal.