After getting Botox in late afternoon, will resuming my physically active job the next morning cause Botox to migrate?

I generally recommend waiting at least 4 hours before resumed any type of physical activity following the injection of Botox.  You should be fine waiting until the next morning.  

While its best to direct this question to your injector, it is not necessary to take a day off work after Botox injections. In our office, the staff and the physicians receive it and go right back to work! The neuromodulator binds to receptors within a matter of hours and at that point, migration is highly unlikely. I usually recommend that patients avoid strenuous activity the day they receive Botox because increasing heart rate and heat will increase the chance of bruising.  You will be fine at work 12 hours later.