Penal Code 288(a), lewd act with a child under 14, is considered a violent felony, which makes it a "strike" under the Three Strikes law. You cannot file a criminal case; only the District Attorney can initiate a criminal prosecution.
In most cases, this charge must be filed before the victim's 28th birthday. By my calculations, you are now 43 years old, so this would not apply.
There is an exception: charges can be filed within one year of the time the offense is first reported to the police. However, the allegation would have to be supported by "clear and convincing" evidence independent of your accusation; the opinion of a mental health professional cannot be used to meet this burden.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like Avvo, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.
There is virtually NO statute of limitations on child-sex cases in California. You can report this to the police, and let them and the District Attorney make the call. They will need some independent evidence. For example, did you consult a therapist or tell anyone else about this at or near the time of the event? And, of course, they will want to know why you are coming forth now and not at some earlier time.