Sore knee possible tendonitis

I started to work out at Curves about 2 months ago & added in the C25K about 2 weeks ago. Last week Friday my knee had a pain in it when I did stairs & I took it easy, iced it & worked out on Monday & Tuesday and now it's painful sometimes just a dull pain sometimes a bit more painful. Do I just Ice & rest it or stretch or what. Has anyone had similar issues any help would be great. If it's not feeling better early next week I"ll go into the Dr & I looked it up on google but get so much b/s to wade through.

Thanks!