sperm-sealed
When the last belated dribbles of cum finally make it out of the urethra, and seal the tip of the penis, or otherwise. Can cause a slight sharp pain in the penis if not thwarted before urination.
Fred masturbated before bed, then later woke up to pee. He hadn't realized that he was sperm-sealed, and was painfully pulled from his drowsiness when nothing immediately came out.