I was stung 3 days ago by a wasp just below my right knee, with severe swelling still, hard & hot to touch, and i itch all over. can i do anything?

Yes, benadryl (diphenhydramine) : 2 tabs every 4-6 hours, make sure you have no contraindication, read the labels carefully, it would make drowsy, so don't drive, then see your doctor asap, ER or Urgent care, need to carry an epipen (epinephrine) in case of future exposure, and GOD forbids a more severe reaction ensues, ask your doctor about it, better to consult an allergist later for more evaluation, good luck