Thanks for posting on HCM,
My advise is you should first of all go to the ER. Cephalexin
is a first generation cephalosporin
antibiotics that could get rid of the infection. The reason why I suggest you to go to the ER is because the infection might be purulent and might require surgical drainage
or cleaning before the treatment with antibiotics and analgesia can become effective. Try applying some ice parks or cool gauze damped in alcoholic solution. Then you can rush to the ER.
Hope this helps