Hi I Had A Rash On My Lower Back And

Hi I had a rash on my lower back and noticed a growing lump in my groine area and now the rash has spread to my thigh and groine area and become worse as well as lumps deeper in the groine causing sharp pains down my leg and pain to the area. I seen a doctor that just said its a swollen lymph node and recomended antihistamines without testing proposed viral infection?