What Causes Pain And Stiffness In The Lower Back After An Insect Bite?

I am a 57 year old female, 5 foot 5 inches, 145 pounds. While in Tuscany 2 weeks ago I was stung by something in the top of my foot. I know because it hurt and started bleeding. Since then I have had numbness in the tip of the second toe on that same foot. I have no other major health concerns and do no take any medications. We also walked quite a bit in Italy. I work out 6-7 days a week but in the past have had lower back stiffness. I stopped running marathons and instead work out with weights and stairmaster/treadmill in the gym to minimize back lower back problems. I also stretch and do yoga which has almost completely eliminated any back problems but I wondered if walking the hills of Tuscany could have irritated a nerve leading to my foot and that toe?