Minor bleeding after radiotherapy is not unexpected. I did read here some time ago the peak time for this in the case of rectal bleeding is 4½ after radiotherapy. Healing after radiotherapy tends to cause the formation of fine fragile surface blood vessels which can break, but this is usually harmless unless you are losing enough blood to become anemic.
However, as said, you always need to report this to your clinicians, because they will need to check it's not another cancer, at least in the case of rectal bleeding or hematuria (blood in urine). I'm not sure what, if anything, they'll do for hematospermia (blood in semen) after radiotherapy.