Take your temperature to see if you are running a fever, even a low-grade one. Then call your doctor's office. One thing you absolutely don't want to mess around with is an infection...so do not feel silly calling.
It is not unheard of to develop a small hematoma post op. It is usually just fluid that has pocketed, and it goes away on its own. I doubt you are feeling the tingling around the screws as they are not near the surface, but probably it is around the incision. You will have sensation around the incision area as it heals.
I'm always telling people to walk, but don't be too enthusiastic about it. Be sure you are resting a good deal of the time. Doing more will NOT make you heal faster. Giving your body sufficient rest is an equally important part of the equation.
Glad to hear you are doing so well.