My friend got a bunch of insect bites on her back recently, and last night, she noticed that a few bruises began to show on the back of her legs just below her buttocks. They feel like bruises, but she did not fall or hit that portion of them in any way. Today, one side is slightly more elevated and tender, and her inguinal lymph node on that side is tender to the touch. She has no fever, and no other notable medical history. What could this be? Should she see a physician?