Without a photo of the damage or the pest we can only guess but it sounds like perhaps flea beetles - they are very tiny, black beetles that jump like fleas and make very tiny holes in the leaves but cause no other harm to the plant and no, they will not cause any disease that can transfer to the fruit. You can find many pictures of them on the web to confirm the ID and get recommendations on treatment if required.

ON the Growing Tomato Forum you will find a FAQ listing the common tomato pests but keep in mind that few of them - with the exception of hornworms - do all that much damage to the plants. Many things can cause holes in tomato leaves but most all holes can be ignored. ;)

Dave