These are on my ranger tandom trailer. One of the wheels, the bearing cap, Im guessing the dust cap on the outside came off and leaked all the oil. At this time I was 150 miles from home. I pounded it back in and refilled with bearing oil for them. And wrapped some duck tape around it for extra protection just to get me home. I believe though that they are still leaking ou of the cap there. But the o ring seal around it is still in tact.

Is there any reason why this popped off? How do I go about fixing it? Is it a quick fix or a major deal?