I have a bug bite that is swollen to about a 6 in diameter. it is hard, red, hot & painful. should i be worried & what might it be? i had thought ant.

Infection: most likely, the bite has become infected. You may have cellulitis or even an abscess. You should be evaluated by your physician as soon as possible

Yes: It appears that this is an infection (boil) which may need to be drained and treated. I suspect that this was likely from a spider bite which is often accompanied by infection which can spread really fast due to the enzyme contained in the venom. See a doctor ASAP.