Hello,
These can be foot blisters, bullous fungal infection or pompholyx if they are itchy. When a foot is hot and sweaty, the sock sticks to the foot. The sock and foot then rub against each other and the inside of the shoe causing blisters to appear.Plantar fibromas are firm, nodular masses which occur as a single mass or in clusters on the arches of the foot.
Wear shoes that fit properly and keep feet as dry as possible.Wearing wet shoes, boots and socks will increase your chance of developing blisters.So change socks regularly.
And use foot powder to help keep your feet dry.If the blisters still persist then pls get it evaluated from a dermatologist/podiatrist.
I hope it helps. Take care and regards.
Could be 'Bullous tinea pedis'. Well treatable with clotrimazole dusting powder.Do consult your doc.