I sometimes suffer form these, almost like boils that havent quite made it yet if you know what I mean…
I only tend to get them if I’ve had a heavy week >200miles, or sometimes after individual long >100mile rides, but there’s no obvious cause, ie: no particular seam chaffing or anything like that. It is worth making sure it’s not being caused by your saddle or clothing though, sometimes it’s an obvious ‘bit’ on either causing pressure or rubbing, but sometimes not.
I find a combination of sudocrem and cleanliness normally rids me of them in a day or three. I know its obvious but keeping clean down there is very important.
I’m sometimes guilty of coming in from a ride, then lounging around with a cup of tea or snack and not having a shower for an hour or two (filthy I know!), I get noticeably fewer issues when I make a point of not doing this. Get home, shower straight away.
Oh, and don’t squeeze! Unless they actually have a head that’s about to go of it’s own accord all you’ll do is inflame and aggrevate it, and possibly worse, push it deeper..