I need some help TMI

While getting my baby ready for bed I noticed some odd looking bump on her leg I have no idea what it could be. Her doctors office is closed this late at night so want to call early in the morning but I don’t know if this is a tic bite or spider bite or if it’s serious enough for a trip to the ER. I could be over reacting but please don’t pass rude judgement on a worried momma.