This is common after receiving a deep tissue massage. Toxins are built up in our bodies and can be held in muscles.
Or you are getting a cold and didn't realize it- and the massage sped up the process.
When getting a massage, espically DT, the fluids and everything else in your body is pushed through your system and muscles. Therefore, when you are "sick", all that "sickness" is getting pushed through too. It would have happened anyway, it was just done at a faster rate.
Stay hydrated. Get a good nights sleep. And just let it's run it's course.
Next time before getting a DT Massage, don't get one at all if you feel the slightest bit sick.