I have a boil about 1 inch from my anus. It is at the site of a former fistula surgery. Should I wait for it to come to a head or seek immediate attention. If so, family doc or colorectal doc to lance?

Colorectal doc. A "boil" at the site of a previous fistula surgery suggests that the fistula has returned. It will probably drain itself easily with hot soaks or baths but the track will persist. Recurrent fistulas can be difficult so a colorectal specialist would be your best option.
Fistula . With a history of fistula formation, it is best to seek immediate advice. If you have a gastroenterologist who referred you for your previous surgery, i would contact him to discuss your symptoms and he will either want to see you immediately or make a referral. Otherwise, get in touch with the colo-rectal surgeon who performed your surgery.