Could be something or nothing, might just be morning mouth of straw dust from snoring all night, but as you mention could be worms but if you have a regular worming programme for him it shouldn't be that (breeding stock should be wormed at least twice year pref invermectin based wormer). He will also be very tucked in around the tummy area and look thinner here too. Check his poo and make sure you clear his pen daily.
Watch out for pneumonia too this time of year, here in the UK the temperatures are up & down like a whores draws so it can be a factor. Check his temperature should be 102 fahrenheit (38.2C). (rectal digital thermometer if poss) Pigs can and do get common colds too just like us humans.
I would suggest keeping an eye on him and his general demeanour (usual self?), if he's eating and doing what boars do generally its probably nothing to worry about.
HTH
Mandy