I cracked a rib when I had bronchitis as a teenager, it was terrible. It's apparently pretty easy to do, so my doctor said. Not much you can do about it, sadly. I wouldn't worry too much about it (even though it's very painful!). It'll probably get better as your cough gets better.

Get well soon!!

BTW there is a shop here in the UK called Jenson's, and they sell DIY type stuff, but also to builders and things. The one near where I live has a poster outside for Thistle plaster products, which always reminds me of you. http://www.british-gypsum.com/products/thistle_plaster_products.aspx The poster says something like "For the best of British, choose Thistle!" so there you go. :-)