Are these real wood, or (like most Ikea stuff) melamine-covered chipboard, with some sort of edge trim? If the latter, you will have trouble reworking the door. Can you post a pointer to the cabinet on the Ikea site, so we can see what it looks like? Does Ikea sell narrower replacement doors and filler panels of any sort?
(looks at Ikea site, kitchen section)
Doesn't look promising. Most of the stuff is chipboard, and not much apparent choice in widths. (Unless maybe the door you have is wide, and you can buy a narrower one, and cut one edge off existing door, so you can shove cut edge against wall so only a factory edge shows. You'd need to add a hardwood rail vertically in cabinet to mount the hinges to, and to catch the edge of the cut-down door used as filler panel.)
I'd be tempted to take the casing off that side of the door opening, and flush it in somehow. How many doors in the room? Changing all the visible door casings might be less labor than modifying the cabinet, if there is absolutely no way to fine-tune reality and slide the whole wall of cabinets down an inch or two. Otherwise, just screw that door shut, and live with reaching around in that corner cabinet. Or add blocks in the cabinet carcass, and mount the door with velcro tape or magnets, so you can yank it off for those once-a-year pots and pans.
-- aem sends, seeing why people diss Ikea....