You can swap that airlock for a new one, but the same thing is probably going to happen again. You really need a blow-off tube. You can make one easily by putting a piece of tubing over the inner stem of a 3-piece airlock and the other end in a bucket or jug of sanitizer. But if you don't have the stuff lying around to cobble together a blow-off tube, you can just take the lid off the fermenter and cover it with some sanitized aluminum foil until things calm down- the CO2 coming off of there will protect it from any nasties that might be floating around, so it doesn't need to be airtight.
Sounds like you have a great fermentation going. Congrats!