My husband (now ex husband) was arrested for domestic assault after pushing me so hard my head hit and broke a table. I didn't press charges at the time because I was afraid of him and under duress from his constant threats, emotional, verbal, and psychological abuse. Years later I was diagnosed with severe and complex PTSD. I've been in treatment and now finally have a voice. Can I press charges now even though it happened 6 years ago?
You can make a complaint to the police: they will decide if they want to investigate the matter.
Depending on which country/state you are in there may be a statute of limitations that means they cannot take action. Notwithstanding, unless there were witnesses apart from him and you this would be an extremely difficult case to get a conviction as there is unlikely to be any physical evidence or contemporaneous records - for this reason, the police may choose not to investigate.
Given the state you are in most states limit (domestic) assault filings between 18 months and 5 years. Also unless your husband admitted guilt there really isn't much the police or prosecutor can do without hard video evidence, even if you were within statute.
As for civil matters PTSD caused by another person is a really serious accusation. There are cases where people have won judgments but these were people brutally abused for years and kidnapped and so on. It sounds that your husband had a temper and there was some abuse but you are relying on one incident that you didn't even press charges on. You could certainly consult a lawyer and if a lawyer took your case on contingency then maybe you move forward.
I would not advise you to start paying a lawyer though as a means of extracting money from your husband based on what he did to you in marriage. There are two things here. First most civil courts understand that most family courts are still more apt to side with women on custody and separation agreements. And second the fact is this should have been brought up during your divorce proceedings and used to discuss splitting of assets and possible future alimony. The fact that you bring this up in addition to your divorce hearings is kind of double dipping in the courts.