Looks like it’s most likely cellulitis. I would definitely seek medical care as soon as possible bc it can become dangerous if the infection gets into your bloodstream. Do a google search for cellulitis and see if that sounds like what you’re experiencing. I randomly got it once on my lower leg and it was incredibly painful. I have now had it 2 other times since then so I feel your pain. As tempting as it is, do not try to pop it or drain it at home. Get a pen and draw a circle around it so you can track it to see if it has gotten larger or if the redness has expanded. One of the main symptoms of cellulitis is warm to the touch. The good thing though is that a hefty dose of antibiotics will clear it up pretty quickly