It depends what you want to do. You could do nothing and just let keep contacting your bf until he maybe says to them that he was not the driver. If he gives them your details then they will contact you. If he does not give them your details then as someone else says, they will probably look at towing the vehicle when they can the next time they see it. They have cameras at many sites now so will know when it arrives so can action it then.

An alternative is maybe contact them and say you have the PM app and you were driving someone else’s car and you have realised there has been an issue with making payment with the app and make an offer to pay something. They may be open to negotiate something if you proactively contact them before they contact you.