Our daughter did the same thing so we put a towel under one side of her neck to force her to tilt her head to the other side, advice from our pediatrician. She still has a moderate flat head but sleeps mainly on her side so is sleeping on her ear! Our doctor said it's fine and of no concern but is monitoring it. If it gets worse, we'll go and see a physio, specifically who deals with kids, they give you exercises to do with your Bub to strengthen their muscles so they use both sides more evenly. Seriously, I wouldn't worry about it yet, there's plenty of time to correct the problem if it keeps happening. The rolled up towel worked for us anyway. HAHA, I call Madeleine our cheeky little monkey too...awesome to know someone else does! Good luck