Hi Dear , As per your query you have lumps under your skin in your arms and you got bite by spider . Well there can be many reasons for symptoms you mention in query like lipoma cyst , skin tag , enlarged vein , abscess , human papilloma virus and swollen lymph gland . In your case it seems to me that the lumps are either due to infection of the skin or abscess . I would suggest you to consult dermatologist for proper diagnosis without any delay . Doctor will examine physically and take take smple for lab test . Doctor may also order blood test . Doctor may prescribe antibiotics at least for a weeks along with anti allergic , anti inflammatory and corticosteroid ointment . Fow now apply warm compresses and take bendryl twice a day . Hope your concern has been resolved. Get Well Soon. Best Wishes, Dr. Harry Maheshwari