Personally, I wouldn't penalize you at all. I'd simply come up with tweaked fluff regarding those particular instances.
I know some people who're able to use things meant to be held/used in two hands use them in one(not quite as effectively[but these people weren't trained either]).
So, if I were a DM, I'd simply let you reskin those items or just assume your character learned to wield such items with one arm. (Shields become some sort of additional plating on one side of the body, or something...)
I know some people who're able to use things meant to be held/used in two hands use them in one(not quite as effectively[but these people weren't trained either]).
So, if I were a DM, I'd simply let you reskin those items or just assume your character learned to wield such items with one arm. (Shields become some sort of additional plating on one side of the body, or something...)