New rainbow flips flops?

I got my first pair of rainbow flip flops last week. they're the single layer ones. after the second time i wore them, i got blisters on the top of my feet from the straps. and also, the soles the flip flop on my right side are getting wrinkly, which is weird because its only on one side. why are they wrinkling? and what can i do to unwrinkle it. and will i always get blisters wen i wear them or do i just need some breaking in time?