What are the possible outcome for being released under investigation?

I work as a private hire driver, and last night i ran into a really weird situation where i picked up someone who i shouldn’t have.

This lady sat in the front of seat and did not want to leave the car as she didn’t book the cab, so i asked her to leave the car, just while we were talking police came in and arrested me for soliciting another for prostitution and then they released me under investigation and asked me to come back after a few days for an interview.

What are the possible outcome?

What should i do next?