Blisters on your feet after a workout may indicate that
a. you need a shoe with a wide toe box.
b. you should wear high-top shoes for ankle support.
c. you may need a special arch support.
d. your shoes do not fit correctly.

Your shoe does not fit correctly. Blisters often mean that the shoe is rubbing places too much when you walk. If the shoe is too small, the shoe will be too tight and restrict your foot, in turn making your toes forced together and heels being rubbed. If the shoe is too big, your foot moves around too much in the shoe, making the shoe to cause blisters.