My cockatiel is bleeding from under his wing?!?

My cockatiel seems to always bleed a little from underneath his wing whenever he flaps them. The pet shop trimmed his primary feathers about 8 months ago but he doesnt seem to be able to fly yet. Whenever he tries to fly he just flutters around on the floor and ends up going straight down in circles. Under his feather u could see his skin and his wing looks shorter compared to the other one..What could be wrong?