I’m scared. Can anyone look at this and tell me what you think

Kayla

Anyone know what this could be? My husband says that it’s been there for a long time(I literally just noticed it today) but it did get darker and says it hasn’t changed over the past couple of months. I don’t have insurance at the moment but am working on it so I can’t go to a dermatologist or anything. It isn’t raised, it’s flat. Ive got to stop worrying so much but I’m scared.

It’s on the back of my thigh.