When the painkillers wear off
It usually happens when you're asleep, or distracted, or comfortable enough to not notice immediately. Then you move and suddenly it all hurts again, and amidst the pain lucid thoughts and worries and concerns return and the weight of everything bores down. Or maybe it's just the pain itself bearing down. Sometimes it's that bad, sometimes it's not, but in the half hour it takes for the new dose to take effect, it can be misery. Pure misery.
On the other hand, sometimes it's a good thing when they do. New pains, you know? Say you fell down the stairs while dosed, or something. Hardly even feel it at the time; might as well have been a stubbed toe. The cracked toenail certainly would indicate that. But then the painkillers wear off. Then you notice the other bruises, and the concussion, and that the toe may have actually been broken...
More painkillers will take care of that.