Moderator here, and this was the question I asked about least and worried about most before mine, so I'm glad you've asked it plainly.
The direct answer, and it matches what Ryan said almost to the day: the operation itself you feel nothing of, because you're under a general or heavily sedated with the chest numbed, and it's over in roughly 1 to 2 hours. Afterwards the ordinary picture is a deep, bruised, tight ache across the chest for the first few days, worst on day one or two, easing day by day after that. It tracks the swelling, which is at its worst in the first 2 to 3 weeks and then fades, and desk work is usually realistic at about 1 to 2 weeks. Almost nobody describes it as sharp. What people describe, once they get past the first week, is stiffness and a vest they're sick of. I set the whole arc out in does gynaecomastia surgery hurt, including the bit that surprised me, which is that the pain lasts about a week and the strange sensations last months.
Mine specifically: first night fine, second day the worst, the local wearing off overnight so it arrived like a bruise ripening. Simple painkillers took the edge off; they did nothing for the tightness, which was the vest and the swelling together, and that was the thing I actually found hard. I was at a laptop by day four and wished I'd waited until day seven. What I'd add that nobody told me is that the second month brought electric zaps and a rawness around the nipples as the nerves woke back up, which was more unpleasant than any of the surgical soreness and which is completely normal. Numbness and altered feeling early on are common and usually settle over weeks to months. The weeks after are in recovery week by week.
What I'm not going to do is tell you what to take or how much, because what they send you home with is a prescribing decision for your operation and your medical history, and the surgeon will have a plan for exactly that. Ask them at the pre-op what they expect the first three days to look like and what they'll give you for it. They answer that twenty times a week.
The one thing to carry in your head instead of dread: ordinary soreness gets a bit better every day, on both sides. One side going tight, hard and MORE painful in the first day, or pain that is climbing rather than easing, fever, heat, a wound weeping, is not soreness, it's a same day phone call to the clinic. That's the only pain that matters, and it happens to roughly one in twenty, which is worth knowing about and not worth losing sleep over.