This will not feel good at first. But persist, and it will help. (and get more comfortable)
Sit comfortably on a chair or on the floor. Cross one leg over your thigh. Fit your fingers between your toes as deeply as possible, and if you can tolerate it, move, bend, flex. Or if not, just hold for a minute. Then, of course, do the other foot. Do this once or twice a day ...
If you wear shoes a lot, try to go barefoot more.
My feet have gotten stronger and more flexible over years of practice, so don't assume this will continue to be a problem.
Yours for flexible toes!