I pretty much only know about PTSD from knowing people who have it. Apparently the trauma can be for many reasons, from physical to mental, and the mental from experiences that were horrible to go through unaffected, to guilt. Regardless, it was outside the sufferer's ability to deal with in a "normal" way. As I understand, treatment depends first on identifying all the triggers, getting the sufferer to recognize them, and then coming to terms with them and their results. Not usually an easy process.
In your case, I don't know if you had PTSD before, or if that even matters. I understand a desire to be safe, and that when one suddenly doesn't feel safe somewhere, it can cause one to feel less safe everywhere. Sorry if there was a student who did not treat you in the best way. Do remember that martial arts tend to be a learning and practice of just that; martial arts. When used to attack, or used to defend, they are combat related. You need to expect some trauma. Simply being blocked in 1 and 3 step sparring will cause your wrists pain until you get used to it, and you will.
If you have it available and can afford it, counseling about your PTSD might be something to consider. If you are already undergoing counseling, I hope you have discussed the incident with your counselor.
Good luck in your studies. There are many advantages to martial arts training. But they may not be as effecting as they could be as long as you have difficulties with PTSD.