While it is the primary- it doesn't hurt a bit. You can even keep the lid on loosely at this point. It is best if you do that you place a cloth over it to keep any little critters out. Sometimes it even helps(but probably not in this case) to give it a gentle stir each day while in the primary. At this point since you have fizzing, it is working and generating C02 providing a protective cap on top of the must-keeping it safe from oxygen. When you transfer to the secondary carboy, put on an airlock and keep it there while it goes through that stage.