Just keep thinking

Every now and then, during the course of writing, you hit on a problem. Something doesn't match up; something doesn't follow. A bit like tripping on a paving stone: with a bit of forethought, a bit of care, you would have seen it coming and you wouldn't have tripped up.
However, some paving stones look perfectly fine - until you step on them and they tilt into a small hole, splashing your shoes and trousers with muddy water, and sometimes even worse things than that.
Yep, sometimes you can't see the problem until you've finished a piece of writing and have read it back. Well, don't panic. Just think. That's all you need to do. Don't gloss over things, don't pass over it, believing: 'Oh, no-one will notice.' They will. The people who will get you published will see, for a start: the agents, the editors. Your intended audience won't get the chance to see.
It's amazing, really, the number of times I think I've hit on a problem which threatens to send my latest story in a different direction to the one I intended it to take. It happens on a regular basis. Complications set in. Life is complicated, after all. But solutions can be found to anything if you put your mind to it.
The answer is to just think. You'll get round it. You'll think of something. Just don't panic, don't get the creeps. Just think. It can take a while for the answer to come through - days, weeks even. But it will.