If I was sexually molested 13 years ago, can I still take legal action?

The answer is maybe. Most statute of limitations expire after a couple of years, but there are expections which expand that limitations period for sexual assault cases, especially if you were a minor.  I would encourage you to proceed forward with the charges for various reasons.  First, you won't know if the limitations applies until you go law enforcement and provide them more details than what you have here to invoke those exceptions.  Second, you may miss an opportunity for some closure if you don't.  Many victims feel relief once the get the charges moving.  Third, even if the charges don't go forward, there will be a record of what he did.  This may not be real helpful right now, but the statistics show that for every one child that is molested, there are usually at least two more that did not report.  Children tend not to report because they have a fear of not being believed.  If and when the next child steps forward, the detective will see there was another complaint similar in nature-- thus improving the criminal case for the next victim.  You may be the voice that someone else desperately needs to hear.