Black Spots on Tail

My son's cornsnake escaped 2 days ago and we just found her, still in his room, hiding up in a chair. While she was missing, he placed her heatpad and water out in the middle of his floor, so she did have access to it, but we have no idea if she used either one. The house is warm (78) but he had is door shut so it was probably something like 60 degrees in there.

Upon inspection, she has black spots on her tail, along the last inch (she is just under 5ft long). We've googled what this might be but would like to know if any of you have experience/advice on anything we should do or expect. As you can imagine, my son is very upset and worried for her. Thank you so much for your help.

I looks like bruising. If it's just the last inch of the tail, I bet she will be fine, even if it falls off (which it doesn't look bad enough to do). I had a milk snake brought to me that had a stuck shed (or 5) on the tail tip, and I soaked it and got it off, but the snake still lost the tail tip. She's still alive today, AFAIK.