It will be important to clean off any glue that has built up by using the least aggresive method possible to avoid damaging the outside diameter of the flow meter. Since the PVC glue didn’t have much of a chance of sticking in the first place, a small plastic scraper could do the trick of getting the glue off…
I can’t image that too much PVC glue can even stick to the ABS. In the event that some is still there, I would carefully cover the ends of the sensor and use some rubbing alcohol on a sightly dampened rag to carefully remove any small glue spots.