nodosum is a type of skin inflammation that is located in a certain portion of the fatty layer of skin.It results in reddish, painful, tender lumps most commonly located in the front of the legs below the knees.
I would recommend a physician/dermatologist’s evaluation. Treatment depends on the confirmation of diagnosis.
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.