The scar

There was a knock.
"I have to study," I mumbled absentmindedly.
The door opened with a squeak. I continued writing my twenty-page essay.
Someone came up to me and hugged me. Only now did I pay attention to him.
I thought for a tiny moment it was my father.
But then I saw his hands and recognized the scar on his thumb. He seemed to have noticed that I had seen it, because he said, "It's okay."
Tears started to flow from my eyes. "I'm so sorry," I sobbed.
He broke away from the hug.
"Do you still have to study?" he asked.
"No."