To be honest, it did not feel like it was too harsh, it just felt like a deep massage. And my neck feels completely fine, no pain. My muscles were a bit sore the day after the massage, but that was more in my shoulders than in the neck even. So I really see nothing wrong with my neck. If anything shouldn't it have helped my symptoms?

If they were too harsh, could they have re-injured my neck? And how long will this flare up or new injury last?
I am quite concerned as I have developed a new symptom (a constant mild nausea/sick feeling) which I was not experiencing prior to the massage. What can I do moving forward to relieve this new symptom. I have tried some neck stretches but it does not help either.