There is a Decathlon store in Ponferrada. This small city is just in front of you, right after Molinasca. It is a short taxi ride from Molinaseca.
If you are in Ponferrada, the store is on the West side of the river. I would estimate it is a good 3-4 km from the municipal Albergue in Ponferrada. I recommend taking a taxi, at about one euro per kilometer from the Albergue to the store.
Decathlon typically carry Salmon, Merrill, and their house brand, Quechua. Their brand, while perhaps not the best in terms of durability, DOES offer excellent value for money. I would recommend them, assuming you tried them on with the socks you intend to wear with them, and walked around the large store for a while. The key, for any hiking boot or shoe, is FIT not size. Wear what works, not just based on numbers.
Remember, your hiking boot / shoe size may be one to two sizes larger than your street shoe size. If you are now having toe problem (blisters or nail loss) your present boots / shoe are too small / short. Also, the size you ultimately buy may be different simply because the boots / shoes were built over a different "last" or metric sizing will vary slightly from UK or US sizing standards. Wear what fits!
If you buy new boots, I strongly advise wearing a microfiber liner sock with a heavy, cushioning, wool sock over it. Also, consider lubricating your feet with petroleum jelly, or equivalent moisturizer, at least until you break the boots in.
I hope this helps.