That spot is very faintly pink- any chance it came from decor or dyed substrate? It doesn't really look like blood to me. Or from prey? Also, blood exposed to air for any length of time tends to turn brown, so that would have had to be very fresh.
I know how concerning it is to see even just a tinge of blood in a snakes urates or stool. It may possibly indicate that your snake has some gastrointestinal parasites* that need to be medically eliminated, so you can expect your vet to need a fresh stool sample to test for this. (*usually from live prey eaten- even before you got the snake)to you for realizing something may be going on & not waiting for it to become worse before investigating.
Have you checked your snake's cloaca for signs of irritation? Sometimes when they expel a hard urate "stone" it causes temporary irritation. Also check for prolapses- that IS a serious issue that requires immediate help.