I’ve not had steroid treatment (yet), but are you sure it’s not a symptom of the relapse you were being treated for, rather than a side-effect of the steroids?
I tend to get painful feet with relapses - in fact, with MS in general!
When I had the relapse that led to my diagnosis, I went to the doctor complaining of a suspected broken bone in my foot! The locum doctor thought I was a whiney middle-aged woman, and fobbed me off. Only later, after being diagnosed properly, did I realise the “broken bone” thingy was probably part of the relapse.