a medical question to pure strangers three days before a three week trip. Ok,,I was a bike mechanic, you can send me $50 for my stellar diagnosis and prescription. You're worth $50 right?
how do you know it's coming from back nerve pain? My friend just had foot surgery on the nerve that leads to that toe. It may be referenced from your back but it could also actually be an inflamed nerve in your foot. I won't presume to suggest a diagnostic method but if you've got a pain that makes you stop doing what you're doing I"d suggest stopping a LOT sooner to shake it out and prevent it from occuring since you probably have more 50mile rides ahead of you on this trip.
Pain requires a recovery period. Whether it's from lactic acid overload or traumatic injury that tears flesh and bones. So if you push until you experience pain you just might develop a cumulative recovery period. Then again you might "work it out" and it'll mysteriously dissapear. If that's the case send me $5.
You don't give any history for this pain, when it occurs, whether other activities affect it, shoes, etc. So from what you say,,ibuprofen or not. Take it easy. Take the effort down and get off BEFORE there's any hint of pain. Stretch and walk before riding, stop before pain announces itself, etc.
When I was 23 I had a ski accident that whacked the hell out of my left patellar tendon right below the kneecap. Couldn't walk for a week. A couple months later in the spring I go to a sports doctor and say "I hurt it",,he said "yes, it's slightly swollen, take it easy and see me in a few months". In a few months I rode from Ogden Utah to Boulder Co. and I made sure to go EASY everyday. In another year I joined a race club and started training and racing but that knee had to be listened to. I HAD to warm up at 50% effort for the first 15minutes. If not i'd get a twinge of pain that would set me back a few hours. If I pushed through the pain I would not be capable of 110% efforts within severe pain. Not capable.
So,,stranger to stranger,,I'd stretch, massage the foot, get off the bike and stretch before pain announces itself,,and take it easy for a couple weeks into a three week trips.