I would give it a chance to go away and if it doesn't, get it looked at. I wouldn't be overly worried. I truly wouldn't. So, monitor it and if it is still there in a couple of weeks, go get your doctor to look at it.
Not enough information but if you tanned a lot, it could be skin cancer. The best answer is to see a dermatologist as soon as possible. I have had skin cancer and it sounds familiar. Let me know how it turns out at ***@****.