I am not a doctor and I don't play one on TV. But I have foot issues and I walk so I see a podiatrist more often than most people. See a qualified doctor, but I will offer some thoughts which you can take with a grain of salt and certainly should not be considered qualified medical advice.
... I'm wearing waterproof hiking boots (should I have gotten something that breathes more?) and lightweight marino wool socks (and sock liners). Might this be more of an issue of needing to break in the boots a bit more? Or toughening up my feet?...
Sounds like you and Dougfitz (below) suffer from Metatarsalgia or perhaps Capsulitis. Both are similar. Both are essentially "over use" injuries.
See the full answer below but try walking with a single pair of socks instead of 2 pairs. One of the more common causes is footwear that is too narrow. Double socks can cause problems.
Your foot will NOT toughen up.
You may want to see your podiatrist about special inserts that can relieve the pressure.
You may need to get wider boots/shoes. You may need to get footwear with thicker/more padded soles
(think HOKA ONE-ONE or ALTRA) hiking/trail running shoes with their ultra thick padded soles.
You may need to do a combination of the above.
When walking longer distances, I get a sensation that my socks have creased up underneath the ball of foot. When it first happened, I took my boot off to straighten out my sock, and found nothing wrong. I subsequently learnt that this is not an uncommon sensation for people walking longer distances. In my case, it has always gone away, but I guess that if it persisted, I would see my doctor about that....
Doug it sounds like you have Metatarsalgia, and there are some treatments beyond ibuprofen. Your description is pretty classical for Metatarsalgia.
Commonly known as a stone bruise, is a general term used to refer to any painful foot condition affecting the metatarsal region of the foot. This is a common problem that can affect the joints and bones of the metatarsals. Basically a pinched nerve due to inflammation.
It commonly affects runners and people with arthritis. It is also common if your shoes are too tight, which may also result from wearing 2 pairs of socks in shoes that otherwise would be the correct size.
Anti-Inflammatories temporarily reduce the pain. Rest can heal the injury, but it can take a long time to make it go away. There are other treatments including orthotics and sometimes surgery.
On the Camino mine started acting up after about 10 days. It was gone by morning with the aid of ibuprofen. By the end of the Camino it was a 24/7 pain. Its been 2 months and a few days since I've been home and it still occasionally bothers me despite the fact that I'm walking very little now as I'm trying to let it heal.