There's a pretty good chance that it is an infection/abscess caused by Fusobacterium necrophorum. It isn't on the bone like lumpy jaw is, but people sometimes call it lumpy jaw anyway. If that is what it is, it should eventually open up and drain. If their body can't completely fight it off, worst case scenario is the infection can spread and kill them, but I think that's less likely. Is it just showing up in one family unit? Are they at a feeding station? If they are coming to feed, you have a perfect scenario to treat them through feed with antibiotics, should you be interested in getting that involved, although coming to feed is likely what allowed the bacteria to spread in the first case..