When I started to take my running seriously an older man told me to look after my feet. The most expensive item that is bought are the shoes. Running isn’t cheap. But when you run quite a bit, blisters do happen. Look after your feet with the appropriate medical treatment. If they do get really bad consult a medical practitioner.
When I started running that tip to look after my feet has seen me through 2 decades of running. After buying shoes and building up activewear, looking after the feet is the next step. Buy good quality socks, these do not have to be expensive. I actually wear two pairs of socks. These aid in cushioning and may also help preventing blisters.
When feet ached or blisters occurred, I have soaked my feet in salty warm water. I have found this method to be very affective in treating blisters.