Does look like it is possibly a scab. I don't see any redness around it which would be a sign of infection.
Do you have other pets? Does your cat have outside access? Do you give regular flea control meds?
Could be from flea bites, general insect bites (my boy likes to lay in ant trails for some unknown reason), plant scratches or fighting with other cats. As long as they look like they are healing well, I wouldn't see a vet personally. Although I have seen a vet for unknown scabs before when the scabs kept multiplying (my boys apparently laid in multiple ant trails over several days, only figured it out when I actually saw him doing it). If they seem to be bothering your cat or not healing, I'd see the vet.