Nobody is accusing you of sexual harassment. They said what they said. You are making some woman uncomfortable. Try to first believe what they said instead of getting paranoid.
You are an intern and probably don't have a lot experience on professional behavior. You might be trying to get be friendly but that is coming out as creepy.
Stop trying to do small talk if the other people don't start small talk with you never. Avoid starting any conversation that don't have a business matter. If the other people in the office start doing small talk to you, then you answer, don't engage the other way around.
Don't try to flirt. Don't stare at woman that are trying to do their job. It is awful to be stared at by men that find you attractive while you trying to go through you day to day to get a paycheck and be back home.
Just accept what they said and try to take this a learning a experience that your behavior does not come out as professional where you are working at the moment. Try to pay attention to that on your next job. That sometimes you might think you are being friendly and people see you as creepy. Again, don't seek a lawyer, you were not accused of sexual harassment, you were accused of lack of professional social skills.