My 3 Yo Male Had Mentioned A Coupke Of Times

My 3 yo male had mentioned a coupke of times he saw blood in his urine. On one occasion i did see a pick what i thought was tissue very small. He also complains that when he gets in the bath that his penis hurts but says it does not hurt when he urinates. A urinalysis showed hazy with mucuous. No other abnormalities. What if anything would cause this. No fever