For a week, i have had a normal gum colored, pain-less sore under my tongue. it feels like a little protruding round sac and looks like a little blister. its more annoying then anything else because it causes me no discomfort. what could this be?

Hard to say: It could be a cyst or an abscess , a lesion of some sort....your description of a bump or sore is vague. How long did you have it? Is it growing ? Etc.. Best to have a dentist take a look, the sooner the better. Good luck and stay safe.

Probably benign: What you are describing sounds like what is called a ranula or mucocele. But it may be a partially blocked salivary gland duct, or an ulcer, or so many other things. It would b prudent to see your General Dentist, a specialist Oral Surgeon, or a specialist Oral Pathologist, to properly identify the lesion and determine if it requires treatment or observation.