Potholes are a County Council responsibility. You can always contact one of your councillors, but there are two ways of reporting potholes (or other highways defects online)
You can go to http://www.fixmystreet.com/ and report it there, This has the advantage that other people can see that you’ve done it. The people at FixMyStreet will then forward it on to County Highways. This is a national website, so if you see a street problem anywhere in the country, they will forward it on to the appropriate department.
Or you can go directly to the County Council website and report it there. This has the advantage that you get a reference number for following it up if nothing happens.