X-Smart and heat creep problem

Hi,I am new to 3D printing and am playing with my new acquired X-Smart. I am using Qidi standard supplied PLA filament.I have done the test example, and that worked fine. Also tried a few other examples.However I have gone for a bigger piece and now I am clogging up every time with heat creep causing the filament to melt ABOVE the nozzle in the feeder area.Any specific advice for a n00b using an X-Smart and having this issue? Might I have reassembled the whole nozzle etc incorrectly?Hints or tips on settings?Thanks