Could they charge me now after they have let me go and if so, what should I do?

Yesterday, I met with a prostitute after exchanging text messages that clearly shows solicitation on my part. When we met, we undressed, did some preliminary, put a condom, but never actually had sex because policemen knocked on the door. They said that apparently, there were noise complaints related to arguing. They asked me a lot of questions but all I said was that I gave her the money for her time and companionship. They found the condom and concluded that there could be my DNA inside. They took my personal info and said that there will be no prison for me or anything, if I would agree to witness. I said okay. They let me go while walking with me downstairs and the principal officer walked with me and gave me a moral speech that I should not do this because I am young and good looking. It was a one-time thing but I don't know what to expect.