If the rear end of the snake looks OK, chances are it just abraded something on its way out and picked up a little blood. This can happen with hard urates, and hard urates can be a sign of dehydration. Be sure to check your humidity to see if it is within proper levels, and always keep the water bowl filled.

If it was something to be concerned about, you would see lot more discoloration. I can't really see a lot in your picture. Just keep an eye on the urates for a while and if you keep seeing more of the same, take the snake to a reputable reptile vet and give yourself some peace of mind