These "warts" which are generally what we call sebaceous cysts, are not often anything to worry about. It is extremely common in older dogs, especially poodles, bichons, and other small toy breeds. As long as one in particular doesn't bother the dog, or continue to grow, there's nothing to worry about. Some people opt to have them removed anyway- which can be done either surgically or in some vet's offices, with something called cryosurgery, which involves no sedation (unless one is very close to the eye) and literally "freezes" the cyst off. That procedure takes only minutes, is inexpensive, and non-painful to the dog. However, chances are high that not only will it grow back, rather quickly, but others may be appearing in time as well. It is best to just accept they are there and keep your eye on them to make sure that is all they are... there... and not growing or bothering your dog. In some instances they can become infected, especially if scratched, and may ooze. If this should occur, cleaning with some diluted iodine (betadine) solution will help clean the mess.
Some people opt to use OTC human wart remover, which is safe topically but don't let your dog lick it off too much. However, these rarely if ever remove them and in the off chance it does, the wart often grows right back.
Best of luck,