Anybody seen anything like this?

Yesterday evening I noticed this on the bottom of my son’s right foot. It looks like blood under the skin. It follows some natural creases/wrinkles. I have massages it and applied heat to it, but no changes. It doesn’t seem to bother him. I’ve never witnessed anything like it, so I’m very curious what it could be.

We did see the doctor today for his 2 month check up. He really didn’t know what it was either. He said if it gets worse he will send him to dermatology.