An idea could be you send an email to the Ponte de Lima Tourist information.https://www.visitepontedelima.pt/en/contacts/ and ask if they could receive and save your luggage for the timebeing untill you arrive. They are in an antique building, a landmark at the Lima river in the center. We experienced the people as very kind and helpfull.
Where are you coming from before arriving in Ponte de Lima ?
From
Casa da Fernanda ?
Btw. I am wondering how you will go back from PdL to Porto.
There is a bus between PdL and Barcelos where you can take the train back to Porto You could ask advise a the touristinformation too because these buses and trains do not run regulairy. Sometime a few times a day.
Btw Ponte de Lima is a beautiful little town , even the oldest town of Portugal and worthwhile staying there and visiting it. But I do not know your itinerary.
Maybe you publish your schedule here .