tibialis posterior tendonitis

After thinking I had sprained my ankle my physio has told me I have tibialis posterior tendonitis and his given me a few exercises to do and also ultrasound massage.

The Pain first came on about 6 weeks ago but after a few days i was able to walk on it again (just) after about 3 weeks it felt ok (ish) that's when I managed to get a referral to see the physio.

As I am starting to use it again I noticed that it seems relatively pain free throughout out the day but as the days moves on i start to get twinges on the inside behind my ankle bump. Am I doing it more harm than good by continuing to walk on it at this point? I dont want to make things worse, by overdoing it.... It only seems to hurt when walking, the pain does not remain if i stand still or sit down...

thanks in advance!:D