you're getting 325mg oxycodone tablets? That doesn't sound right unless some homemade/street manufactured, and they're making pills that 1-2 would likely cause fatal OD in anyone without a high tolerance to opioids. .
Either way, only taking 1/6 of your average dose will probably put you in some mild withdrawal, and noticeable shift in mood. I'm not sure it will just pass in a few hours... unless you are back to your normal dose, chances are things will get a bit worse for 1-2 weeks before they start to improve. You can taper down, but most say that oxy isn't the best opioid to taper with due to shorter half life and constant need to re-dose in smaller and smaller incriments- none the less, it can be done. Depending on how fast you taper, it will be unpleasant but nothing compared to going cold turkey.
The problem is actually sticking to your taper when the dark clouds are looming over your head and you have a stock of sunshine laying around. At some point you just have to accept it and find other ways to work through the difficult times. Cognitive behavioral therapy is my go to, as it's something you can do on your own and in your head, while at work or in public even. It takes a lot of practice, and generally helps to have someone to help guide you, especially at first. Exercise is great as well, but I'd go very easy if experiencing flu like symptoms.
If there is nothing else bugging you, it's def the drop in oxy. If there is other things bugging you, the drop will probably amplify it.