Hello,
Painful blisters which are spreading can be due to bacterial infection. I suggest you to get a culture sensitivity of the fluid from the blisters. Then you may need oral antibiotics or intravenous antibiotics.
Apply warm compresses, Neosporin ointment and calamine lotion and avoid messing with it. You can take anti-inflammatory pain killers like ibuprofen or acetaminophen. If the lumps persist then it will be best to get it evaluated from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
These are caused by 'atyopical mycobacteria' possibly M. marinum or staph. .Antibiotics are the mainstay treatment.