Perhaps going-up on your tippy-toes, good leg first, then bad and hold that position (with surface nearby to hold-on) to gently strengthen the foot between now and your physio appointment may help with the stairs issue and do try and walk down the stairs normally rather than good leg first if possible.
That's really good you've identified the stairs as a problem, you should try and make a note of other activities that are affected by it before your physio appointment so that they'll be able to help you to get back to running again.