Can trace of blood appears in urine because of inguinal hernia? Sometimes while sitting have a dull pain around left scrotum.

Not related. Trace of blood should be evaluated to rule out kidney, bladder or urethral problem. Dull pain in left scrotum can occur with varicocele (feels like bag "bag of worms" in left scrotum when standing erect). Your pain could be related to urethritis, which might also be responsible for blood trace.