Last week while putting in some new floor boards, a nail went through a water pipe. A plumber came (a poor one), bled a radiator and fixed the leak. Ever since, whenever I put on the central heating the boiler rattles loudly, when switching itself on and off. The rattling continues in pipes around the house. I have used a key to release air out of the pipes but this has not improved it. The rattling stops after a few hour. Any suggestions?