Did you try it before you purchased it? I let my clients do that to see how they like the case. As long as it's not scratched/marked/damaged and you did not install the screen protector (if you have the commuter) then you'll be able to return it.
The phone's fairly compact to begin with... if it's the defender then I understand your concerns but if it's the commuter series then you must have pretty small hands. :P