@Kez welcome to the fallen brigade.
It happens.
I fell badly coming out of Logrono and somehow kept walking to Najera...then had a series of quite short days until Belorado. (I
really shouldn't have gone that far on day 1, but was running on adrenaline.)
As others have said, I wouldn't decide just yet. If it turns out that you
have to skip anything, what to skip is
so personal. Some people hate the Meseta but I wouldn't miss a single step of it. Others love cities and would jump ahead, but I'd pass...just 2 examples.
You know yourself, we can only give our multifarious opinions.
So here's mine: as you're not a city person, you could get transport from Mansilla de las Mulas to Leon, then Leon to Astorga, making up 2-3 days. Or a train from Sahagun to Leon or even all the way to Astorga, jumping ahead 3-5 days.