I am not an attorney nor do I play one on TV.
The suggestions I have are what come to mind and are not based in law.
First, I would document everything you can remember about that incident and any others which may have occurred. If you can remember the dates and times, include that as well. Also include in your documentation the comment you made to a co-worker, why you made it (she said she was pestered for a date, etc.), and what happened afterward.
Consultations with an attorney are free. You may want to call an attorney who specializes in workplace relations, sexual harrassment or both (or something along those lines). Give as much information as you can so the attorney can give you as complete an answer as possible.
You may also want to contact the Department of Labor and ask them what steps you should take. You can also go online and find the site for the Department of Labor that corresponds to your state. You should be able to find the specific laws and regulations regarding sexual harrassment in the workplace. This site
might also be helpful.
Document EVERYTHING. Every comment by your boss or coworkers, snickers, etc. Include dates, times, places. Also include who else was present when certain things were said and / or done. Also keep track if you suddenly start receiving less than favorable treatment or performance reports, especially if they are a significant departure from previous assessments of your performance.
I wish I had more specific information for you.