Liquid nitrogen on little pimple

I went to my dermatologist for a check-up and some refills (May 27th). While in my visit I told me him about this little bump on my cheek that it looked like a pimple, and it has been there for almost 3 months or more. He immediately sprayed liquid nitrogen on my cheek. After 2 hours or so when I got home it became a blister. The next day worried about it..I went back to my dermatologist...and he told me the blister is normal since he froze my face at low temperature. He then applied Aquaphor - petrolatum ointment on the blister and told me to not pick it or anything. Today (29th) I woke up and the blister was popped..not sure how...what should I do? Should I put a bandage or just keep applying the petrolatum ointment on the affected area? Will it leave a scar? X_X...