I'm a female and just this past Saturday I woke up with a red bump or knot under my breast and it was slight bruised. So I figure maybe it's a boil and here it is Monday it hasn't bust but it started to pain bad, tingle, there is a huge welt around it. I'm not sure what it may be, some say maybe a spider bite. I'm not sure Please help.

There's no way for us to tell you what it is either, a doctor will have to look at it. It could be a cyst, it could be an ingrown hair, it could be a bug bite, it could be a pimple, there are many possibilities. You'll need to see your doctor.