Constant running pump?

Please can somebody help?
I have a Baxi Solo 3 Boiler, everything was running fine and one night a loud clunking noise was coming from the CH system (yes I agree air) after then I turned the pump speed up to push the air around and out and it worked as I heard the air (bubbles) coming out from the tank.

Ever since then my Grundfos 15-60 pump will not turn off unless I turn it off by the fuse? Also I have turned the speed back down to 2.

Any help please

Andy