Thank you for your query on Healthcare Magic.
Do not panic and be relaxed.
The pink spot in the diaper may be due to some other reason from the external sources like from stool or the other thing.
Blood in urine in infants is a rare phenomenon.
You said you believe that his uterine is blood tinged - I think you meant to say it is urethra
is present in girls and it is female genital part.
and apprehension can be ruled out by doing complete urine examination of the child which rules out the blood in urine.
Therefore consult your Pediatrician
for the examination and for the investigation of the urine sample.
Hope I have answered your query.