Following an erection, sexual arousal may result in slight semen buildup in the penis. The soft dribbles occurs when the penis goes flaccid and this buildup of semen trickles out of the penis. This occassionally results in itching, tingling, and/or tickling sensation at the hole. A male may manually eject the semen by gripping the shaft and squeezing as he pushes along to expel the semen.
After I woke up with morning wood, I had the soft dribbles.