I believe it's some sort of viral symptom most likely, but the current 'official' belief is 'it's caused by pecking through mesh'.
This rather weak explanation is used is despite the fact that it spontaneously occurs almost as a rule only to a certain age group, all at once, and mixed-age flocks kept together in which all birds are pecking through mesh don't exhibit it again after that first time. It appears contagious, but that said very healthy birds don't get it and even very unhealthy birds don't seem to die from it or suffer any other symptoms.
I think it's some sort of papilloma or herpes virus, personally, as it matches symptoms known to be caused by that family.
Generally it causes a lump, usually white and appearing to be lodged within the beak at the junction of comb and beak; this lump falls out after a while, leaving a hole in the beak which slowly heals. It doesn't recur in any birds I've seen even if they go on to spend the rest of their lives pecking through mesh. It always occurs in the exact same place on every bird and always looks like they're trying to grow some kind of horn, lol.
Mine never had it, not one, and I've raised many hundreds of chooks for years, with plenty of them being keen to peck through mesh, some to the point of cutting themselves.
I wish some vet would be willing to test this and find out what it really is. It defies logic to state that it's some sort of magically isolated and perfectly-identical-in-all-individuals damage caused by pecking though mesh; birds who are clumsy with mesh always cut their combs and wattles as well, never make a perfect bump in the exact same location on all birds of the exact same age group. But, that's the 'official explanation' for this.
Long story short, it's highly unlikely to kill her or make her sick, and it will resolve itself given time.
Here's some info on papillomas in general. There's quite a few sites with articles dealing with papillomatosis in birds, and they all refer to beak lumps, usually being around the midline, and of the same appearance as I've seen in chooks; chooks are also known to get papillomas among other viral tumors.
Here's some info:
Quote from above source:
Some sources blur the last distinction there, that papillomas of the skin even exist (despite it being a well known fact) and define papillomas as being restricted to mucosal tissues. That's just plain incorrect. Yet some experts still espouse it.
It looks a lot like the same sort of bumps in the links above. Some people believe these bumps are from injuries on sharp objects such as metal feeders/waterers or fencing, or from a virus. If you read those links, it seems that no one has ever found out for sure what they are dealing with, but many of these simply fall off.
Probably the same thing, but of course my guesstimate is no guarantee.
You can get the lumps tested to find out what they are; that'd take some looking into since my best guess there is that you'd have to go to a vet for it. May or may not be expensive.
However since it looks the same as the top lump, similar anyway, it may be caused by the same thing, and as Eggcessive said, many of them just fall off.
There's always some potential it may be something serious and you may be the one who cops it where others skated through with no complications, so if you are worried about it and able to afford a vet check it may be worth getting those lumps tested for herpesvirus etc.