Skin Problems Scab?

I was getting ready for bed last night, when i heard a loud spueal. I know for a factmit was from Truffes, my younger piggy. I took him out for a while to just pet him, ao he gets relaed, when i felt a bump. I ook him into the light and saw it looks like a scab. I was about the size of a pencil tip. I have no idea what it is. He has been scratching lately and I am etting ready to treat him for ivermectin, but i dont know if this has anything to dowith that. PLease help!