Injury to Snake

Question
We have many beautiful Gopher Snakes living our yard. Yesterday I came upon one who appears to have been injured (maybe abused?). The very end of his tail is knotted and non-functional. It's hard to the touch and he/she makes no movement when that area is touched. He/she also has a muddy mark a few inches above the end of that could be about the size of a bike or motorcycle tire. Here's my question: Is it possible that the snake tied up its own tail because of the injury and that the dead portion will fall off allowing it to return to normal?  Or is this a case of someone abusing this creature? I found him/her this morning curled up in a safe place, but her tail from the muddy pat down was exposed.  It's as if it doesn't know that part isn't hidden.  I care a great deal for the critters in our yard and don't want this one to be injured furtehr because of this.  Thanks for your time.

Answer
I have actually seen snakes born with their tails knotted so that alone wouldnt really be an indicator of whether or not it's injured but if it acts like it's injured then it most likely is.  The tail would not return to normal if it fell off though to answer that part of the question it would always have a stubbed tail.