The thick layer you are seeing is the krausen and it means the beer is fermenting. Most likely you have a leaky seal in the lid and the gasses are escaping from somewhere else, not a problem and can happen. Give it another few days and take a gravity reading if you want or leave it alone for 10 days or so and then check to be sure the gravity has dropped.
Nothing Left to do but smile and drink beer.....
The Commune Brewing Company-Perfecting the "art" of beer since 2010