Seems to me that if the gear won't retract, then there is a problem with the gear system. Part of that system is what keeps the gear down (and locked). So if you don't know why it wont retract, seems to me that you can't be certain it will stay down and locked. Granted, there's no way a single engine Cessna main is going to collapse on the ground, but nose certainly can. And if you go flying, (depending on what caused the failure) it's possible for the mains to come unlocked in flight and then you have a problem. So to my mind, until you know something about the problem, I would be hesitant to go flying around.