Yogi's got it right as far as it's fine to let all kinds of oxygen into your must in the early stages.
Last time I was out of bucket lids that were either loose or punched for an airlock, I tried sealing it with the intention of making sure I poked it a couple times a day, but it got going REALLY FAST (for once!!) and when I saw the lid starting to deform from the pressure, I ended up just sitting the lid on top of the bucket without sealing it, until it was about halfway done its sugar, by then one of my other bucket lids with an airlock hole was free so I transferred it over.
"The main ingredient needed is 'time' followed closely by 'patience'." - The Bishop 2013
"Good grief! If someone wanted to murder you, all they would have to do is ship you a 55 gallon barrel of honey and watch you document working yourself to death!" - Vance G