@ladybird64 I am concerned that you could be trying too hard. Not knowing how recent the cancer treatment, or anything at all about it, I don't know what to say. I would not advise anyway, as I am not medically qualified, but it seems that you would be best advised by doc, regarding the blisters and the level of activity.
I know how frustrating it can be to be immobile after surgery, and have also been restricted in mobility for over 20 years after becoming disabled in an accident. The whole purpose of these threads, started by jamrox is to make us think about ways to increase activity. When I first started, much of my activity was chair based, out of necessity. I even claimed knitting as my activity once.
Softly, slowly, gradually increase activity. Find a level that does not leave you exhausted. Don't set the goal to unachievable.
I should follow my own advice. Stepping out today, as much as I enjoyed it, ended with me having a fall. I do that from time to time, usually when I push myself too far. Nothing hurt but my dignity, but I expect to hurt a bit tomorrow.
Take it easy, be good to yourself, and do not neglect those blisters.