You need a lawyer to help you with any issues that arise during this investigation. They may ask you to come in for additional interviews or to give a DNA sample, etc. They may get a search warrant. You need to be thinking about how you can defend yourself against these allegations. If the 4 year old has said something remotely sexual about you, and you have described it to the police as a "misunderstanding", you are most likely going to be arrested. You can't wait until you've been arrested, 'cause you aren't likely to make your bail for child molestation charges. Get an attorney now. If you don't have the money, find a way to borrow it from someone else, or get your priorities straight and find the money in your current budget.
First, don't say anything else in this forum, because like with the Miranda warnings, anything you say can and will be used against you if you act contrary to the purpose behind those warnings. Second, I strongly advise that you refuse to speak with the police any further, at least not without a lawyer present. While you may not be able to afford an attorney right now, I advise that you sit down with a criminal defense attorney at least for a consultation and get advice on how to proceed from here. If you get charged, then you may qualify for a public defender to represent you.
You absolutely need an attorney. I understand that it could be a financial burden to retain an attorney, however you should at the minimum consult with a local criminal attorney to review your legal options. Good luck.