Helpppppp

So I went to go get a pedicure today, and I just noticed this in the shower while I was taking my sandals off. She put the water hot hot & I had to tell her to stop it cause I couldn’t handle it. Could it be a burn mark? It’s not dirt cause I’ve rubbed it so many times already with soap and water. What could it be? It just showed up today. It’s not a bruise either cause it doesn’t hurt.