Two US friends had similar experiences. The one who had to stop in Astorga decided to take a room for a week and enjoy the city square, meeting other peregrinos and chilling out. She took some physiotherapy locally and spoke very highly of the care, as well as of the assistance from locals.
Another, whose complaint sounds like yours, stopped in Burgos and, after some reflection, went to a village near the sea where she stayed with a retired teacher, who coached her in Spanish in the morning. As her Castellano improved, she came to enjoy herself and appreciate meeting people locally, inserting herself into the two local choirs for the rest of her stay.
I met a German doctor pilgrim whose knee gave out, and he simply went home, as did another US pilgrim who found the xperience of the Camino too emotionallyintense for her.
If you have to hang around for a week, Burgos might be interesting, as it has a number of remarkable sights and you will not be bored. English-language books and papers are available there. Ditto for Leon (I have a suggestion for a place to stay there-- PM me for details).